Update protobuf to 4.21.3#1937

pyup-bot wants to merge 1 commit intomasterkragniz/python-etcd3:masterfrom

pyup-update-protobuf-3.17.0-to-4.21.3kragniz/python-etcd3:pyup-update-protobuf-3.17.0-to-4.21.3Copy head branch name to clipboard