chore: update protos to circa 2020-05-17 (#50)
chore: update protos to circa 2020-05-17 (#50)

Use the same commit we are using for the Bazel builds in
google-cloud-cpp. AFAICT, there are no significant changes, but it
is good to keep both build systems in sync.
googleapis/cpp-cmakefiles,googleapis/cpp-cmakefiles,googleapis/cpp-cmakefiles