doc: update patch release instructions (#7525)
doc: update patch release instructions (#7525)

Fixes: #7465

The instructions for creating a patch release needed to be updated since
we now use versioned inline namespaces that include the major, minor,
and patch numbers. The rule of thumb is that the ABI baseline files need
to be updated anytime a version number changes.
googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp