Fix buck build, remove java_test.source_under_test
Fix buck build, remove java_test.source_under_test

This parameter is also not required any more after buck upgrade
in Gerrit.

Change-Id: I32d9e6dcc49c3af0c32033824ed673f82270e9d7

GerritCodeReview/plugins_delete-project,GerritCodeReview/plugins_delete-project,GerritCodeReview/plugins_delete-project,GerritCodeReview/plugins_delete-project