Merge pull request #6755 from alvasw/apply_proto_tasks_only_to_main_source_set

proto: Apply proto tasks only to main source set

proto/build.gradle

@@ -38,6 +38,6 @@ protobuf {
         }
     }
     generateProtoTasks {
-        all()*.plugins { grpc {} }
+        ofSourceSet('main')*.plugins { grpc {} }
     }
 }