README.rst: use `protos` instead of `proto` (#2706)
README.rst: use `protos` instead of `proto` (#2706)

The documentation for `go_proto_library` states that the `protos`
attribute should be used instead of the old `proto` attribute.
bazelbuild/rules_go,bazelbuild/rules_go,bazelbuild/rules_go,bazelbuild/rules_go,bazelbuild/rules_go