FindProtobuf: Fix new version number scheme
protoc v3.21 still reports libprotoc 3.21.x instead of omitting the "major" version number. protoc v3.23 for example reports libprotoc 23.x when queried for its version number.
See !8574 (comment 1386445) for the initial discussion.
Backport: release
Topic-rename: FindProtobuf-version-schemes
Edited by Brad King