Follows-up {T263872}.
The WMF-specific `extensions/WikimediaMaintenance/refreshMessageBlobs.php` is now identical to core's `purgeMessageBlobStore.php`. There is no longer a use for the WMF-specific one to my knowledge.
According to Codesearch we have:
* [X] Outdated mention in `scap.git: scap/main.py`
** https://gerrit.wikimedia.org/r/c/mediawiki/tools/scap/+/831628
* [X] Else branch in `scap.git: clear_message_blobs`. Flatten to unconditional call? Yes.
** https://gerrit.wikimedia.org/r/c/mediawiki/tools/scap/+/831628
* [X] Shell invocation in `puppet.git: scap/l10nupdate-1`. I believe this has been unused for a long time, probably the script can be removed entirely (ref {T158360}).
** https://gerrit.wikimedia.org/r/c/operations/puppet/+/896318
* [ ] The script itself in `WikimediaMaintenance.git: refreshMessageBlobs.php`
* [ ] Special handling in `wmf-config.git: multiversion/MWScript.php`. This should be done last, after the actual script is deleted.