Protocol: bumping to v14.8

Taken from Gitaly v14.8.2, the most notable difference for us
is the removal of the `CommitService.CommitsBetween` RPC method.

As we've had problem with grpcio/grpcio-tools 1.44, we're pinning
to 1.42, the same version used in the Rails application in GitLab
14.8. This does change the resulting stub modules.
4 jobs for !97 with topic/default/gitlab-14.8 in 3 minutes and 25 seconds (queued for 1 second)
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