Remove unnecessary jar packages

flink-connector-redis using embedded-redis (version 0.6) for test. Although the scope is specified as test in the pom file, embedded-redis depends on common-io (version 2.4). Due to the transitivity of the dependency, the flink-connector-redis package depends on the unused common-io (version 2.4).
The common-io jar package needs to be excluded from the pom file.