Since we aren't publishing the package anymore the version config in the pubspec does not have meaning.

Since we roll into the SDK by SHA instead of version tag, the headers in the CHANGELOG don't have meaning. Overall without a publish there isn't a meaningful way for end users to find the relevant changelog entries for the SDK version they are using.

We should stop populating these values.

@pq - do we have some kind of process for editing the SDK CHANGELOG when we update the SHA configured in DEPS for the SDK?