commons: avoid use of Guava beta APIs in StringSort

[INFO] Compiling 33 source files to /home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/target/classes
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:187: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
                writer = Files.newWriter(idFile, charset);
                              ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:187: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
                writer = Files.newWriter(idFile, charset);
                         ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:213: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
            CloseableIterator itr = new CloseableIterator(Files.newReader(sortedFile, charset));
                                                               ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:213: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
            CloseableIterator itr = new CloseableIterator(Files.newReader(sortedFile, charset));
                                                          ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:225: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
            Closer closer = Closer.create();
            ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:225: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
            Closer closer = Closer.create();
                                  ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:225: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
            Closer closer = Closer.create();
                            ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:228: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
                closer.register(new Closeable() {
                      ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:234: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
                closer.register(writer);
                      ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:236: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
                    closer.register(citr);
                          ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
/home/jenkins/jenkins-slave/workspace/Apache Jackrabbit Oak matrix/Ubuntu Slaves/ubuntu/jdk/JDK 1.8 (latest)/nsfixtures/SEGMENT_TAR/profile/guavabetachecks/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/sort/StringSort.java:239: error: [BetaApi] @Beta APIs should not be used in library code as they are subject to change
                closer.close();
                      ^
    (see https://github.com/google/guava/wiki/PhilosophyExplained#beta-apis)
11 errors