Build of 6.1.0-post branch and v6.1.0 tag fails

Building the 6.1.0-post branch of v6.1.0 tag of this repo fails with:

```
[ERROR] Failed to execute goal io.confluent:resolver-maven-plugin:0.5.0:resolve-kafka-range (default) on project common-parent: : MojoExecutionException: Could not find any ccs-kafka artifacts. -> [Help 1]
```

Issue appears to be with Maven resolver plugin, which is looking for `6.1.0` artifacts instead of `6.1.0-ccs`. The following is a workaround:

```
mvn install -Dskip.maven.resolver.plugin=true
```

However, this should ideally be fixed in `pom.xml`.