RELEASING.md: Bump protobuf version to match build.gradle

[ejona86]

For 1.40.0 the protobuf version was bumped to the latest version, which
we hadn't tested at all. We want to bump to the version used in the
release.

[YifeiZhuang]

I see, we are still using

grpc-java/build.gradle

Line 60 in 25022f6

protobufVersion = '3.17.2'

And also need to update in examples?: https://github.com/grpc/grpc-java/search?q=protobufVersion

And s/protocVersion/protobufVersion? where is the protocVersion come from? I can not understand it.

[ejona86]

There are two different versions of protoc we have in our repo at a time:

• The version we are actually using. This should be the same for the entire repo and applies to examples as well
• The version referenced in the README, which is the version the last release used

It is not appropriate to update the protobuf version being used as part of the release process. We want to continue using what we have been testing for a while. We do need to update any documentation though, and that's what is discussed here.

I said protocVersion because that's the variable that matters. Yes, the code happens to have protocVersion = protobufVersion, but that isn't always the case.

[YifeiZhuang]

Yea.
I did feel unclear when I was here doing the last release.
Just talking about document, we shouldn't use the new version, both the master and 1.40 should be using 3.17.2 in its documentation.