Avoid using unspecified keyword args where possible

src/ruby/lib/grpc/errors.rb

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

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

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

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

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

src/ruby/spec/generic/active_call_spec.rb

src/ruby/spec/generic/client_stub_spec.rb

src/ruby/spec/generic/rpc_desc_spec.rb

src/ruby/spec/generic/rpc_server_spec.rb