Fixed resolution problems of gobblin-parquet

[mockitoguy]

'com.twitter:parquet-protobuf:1.5.0' (including higher versions) is not resolvable from MavenCentral because it's missing some of its transitive dependencies. This makes the 'gobblin-parquet' module also not resolvable from MavenCentral (e.g. 'org.apache.gobblin:gobblin-parquet:0.14.0' does not resolve from Central as of today). To fix this, I suggest making parquet-protobuf dependency 'compileOnly'. This will ensure that 'gobblin-parquet' is cleanly resolvable from Central.