After releasing 1.24, clean up typeshed compatibility code

[nipunn1313]

Typeshed has some compatibility code (see typeshed#4833) for mypy-protobuf 1.23
After 1.24 releases and is out for a few months, clean that stuff up in typeshed

[nipunn1313]

Fixed by python/typeshed#5753

[nipunn1313]

and python/typeshed#5754