Pin the version of protobuf for Tink Python.
Pin the version of protobuf for Tink Python.

Installing protobuf without pinning the version will install 4.20 which make some of our tests fail.

PiperOrigin-RevId: 451172163

google/tink,google/tink,google/tink,google/tink,google/tink,google/tink,google/tink,google/tink