Merge pull request #11859 from nathanielmanistaatgoogle/gitignore

Narrow src/python/.gitignore to only what it needs to ignore.

src/python/grpcio_tests/.gitignore

@@ -1,5 +1 @@
-proto/
-src/
-*_pb2.py
-*_pb2_grpc.py
-*.egg-info/
+/src/