Un-hide force_key_update / initiate_key_update

[gretchenfrage]

See #2097.

Note: initiate_key_update (the one in proto) is called from various places internally, which is the primary reason for differences in their names and comment.

[djc]

Hmm, CI seems stuck on this one? Maybe rebase?

[gretchenfrage]

Hmm, CI seems stuck on this one? Maybe rebase?

Nothing to rebase over ATM.

[phoenix@leliel:~/repos/h3stuff/quinn]$ git fetch upstream main
git From github.com:quinn-rs/quinn
 * branch              main       -> FETCH_HEAD

[phoenix@leliel:~/repos/h3stuff/quinn]$ git rebase upstream/main
Current branch force-key-update-public is up to date.

[phoenix@leliel:~/repos/h3stuff/quinn]$ git push --force origin force-key-update-public
Everything up-to-date