Remove nonces in maint/repair.php

[nacin]

Since salts (and now keys) fall back to the database, a user with an options table down for the count often won't be able to repair the database. That's because maint/repair.php has nonce checks.

I chatted with ryan about this, and he confirmed that there definitely should not be nonces here.

A friend of mine just ran into this. Luckily I knew exactly why he was seeing "Please try again" over and over again, but most users do not have core developers as neighbors.

See also #20779, where we can encourage extra security on maint/repair.php by seeing if they actually have a complete set of keys in place.

[ryan]

Looks good.

[westi]

Looks good here too.

[nacin]

In [20953]:

Do not perform nonce checks in maint/repair.php.

If the options table is damaged and the keys/salts fall back to the database,
the nonce will never validate.

fixes #20780. see #20779.