chore(deps): update dependency protobuf to v3.18.1 (#1008)
chore(deps): update dependency protobuf to v3.18.1 (#1008)

Co-authored-by: Dov Shlachter <7784d487578ade2c73937fc6777172a443d2d9a9@google.com>
googleapis/gapic-generator-python,googleapis/gapic-generator-python