Removes Google username from TODOs, removes defunct TODOs

src/ruby/bin/interop/interop_server.rb

src/ruby/ext/grpc/extconf.rb

src/ruby/ext/grpc/rb_completion_queue.c

src/ruby/lib/grpc/generic/bidi_call.rb

src/ruby/lib/grpc/generic/rpc_server.rb

src/ruby/lib/grpc/logconfig.rb

src/ruby/spec/client_server_spec.rb