potentially unnecessary class inheritance in the ClientInfo class

[rosiezou]

I noticed that there are two implementations of the ClientInfo class inside the api_core repo. One in google/api_core/client_info.py and one in google/api_core/gapic_v1/client_info.py. The ClientInfo class in the gapic_v1 directory inherits from the ClientInfo class in the parent directory, and it appears that there are no other references to the to_user_agent function except for its invocation in ClientInfo.to_grpc_metadata in gapic_v1/client_info.py. Could this function and other member variables in the parent class be folded into the child class?

[vchudnov-g]

Thanks for noticing this! We'll take a look when we next get a chance to inspect our architecture.