update supported protobuf version

[evanstade]

perfetto is not compatible with newer protobuf, for at least one reason: its overrides of google::protobuf::compiler::MultiFileErrorCollector are no longer functional; see this change and this change.

In Chromium this forces us to revert the second change in our copy of protobuf to support perfetto.

[LalitMaganti]

From what I understand Chromium is on the same version of protobuf as us. Is that uprev happening on the Chromium side?

[evanstade]

Yes, Chromium is trying to uprev to pb 29.3. This is the only breakage related to that which I have noticed thus far, which is fairly lucky :) This is the workaround. After Perfetto is updated and rolled in Chromium we can simply remove that patch.

[evanstade]

I have also noticed that trace_processor_shell should probably have a dep on ../../gn:protoc_lib because it uses Parser which is part of the pb compiler. For some reason, Chromium currently pulls Parser into protobuf_full, however I suspect that Chromium should not do so. Making this change in perfetto and will allow Chromium to fix this oddity.