When determining expansion service jar, depend on Maven coords instead of Gradle target

[damccorm]

For example here: https://github.com/apache/beam/blob/release-2.24.0/sdks/python/apache_beam/io/kafka.py#L107

Maven coords is more stable than the Gradle target name so it's better to depend on the prior. See [1] for details.

[1] https://issues.apache.org/jira/browse/BEAM-10986

 

cc: [~robertwb] [~bhulette] [~kenn]

Imported from Jira BEAM-11026. Original Jira may contain additional context.
Reported by: chamikara.