protobuf has removed the definition of this macro as of commit
1595417dd3859bbff7d3d61ad0b6e39044d47489, so the invocation of this
macro in protobuf-c breaks the build when building agaist the protobuf
22.x or 23.x series.
Simply removing the macro invocations seems to be safe and doesn't break
the build on Debian's protobuf 3.21.12 nor Debian's protobuf 3.6.1.3.
ad48868dfe