fix: try to gen proto with same environment

Author: mudler

backend/python/parler-tts/Makefile

@@ -35,5 +35,5 @@ protogen: backend_pb2_grpc.py backend_pb2.py
 protogen-clean:
 	$(RM) backend_pb2_grpc.py backend_pb2.py
 
-backend_pb2_grpc.py backend_pb2.py:
-	python3 -m grpc_tools.protoc -I../.. --python_out=. --grpc_python_out=. backend.proto
+backend_pb2_grpc.py backend_pb2.py: protogen
+	bash gen_grpc.sh