Quickstart E2E test archetype version is hard-coded

mvn archetype:generate                                   \
    -DarchetypeGroupId=org.apache.flink                  \
    -DarchetypeArtifactId=flink-quickstart-${TEST_TYPE}  \
    -DarchetypeVersion=1.6-SNAPSHOT                      \
    -DgroupId=org.apache.flink.quickstart                \
    -DartifactId=${ARTIFACT_ID}                          \
    -Dversion=${ARTIFACT_VERSION}                        \
    -Dpackage=org.apache.flink.quickstart                \
    -DinteractiveMode=false