Optimize the assignment of scopes

Author: lidizheng

gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/grpc.py.j2

@@ -126,8 +126,7 @@ class {{ service.name }}GrpcTransport({{ service.name }}Transport):
         Returns:
             grpc.Channel: A gRPC channel object.
         """
-        if scopes is None:
-            scopes = cls.AUTH_SCOPES
+        scopes = scopes or cls.AUTH_SCOPES
         return grpc_helpers.create_channel(
             host,
             credentials=credentials,

gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/grpc_asyncio.py.j2

@@ -61,8 +61,7 @@ class {{ service.grpc_asyncio_transport_name }}({{ service.name }}Transport):
         Returns:
             aio.Channel: A gRPC AsyncIO channel object.
         """
-        if scopes is None:
-            scopes = cls.AUTH_SCOPES
+        scopes = scopes or cls.AUTH_SCOPES
         return grpc_helpers_async.create_channel(
             host,
             credentials=credentials,