* Automatically fix all tags with incorrect counts during daily
maintenance (previously only tags with negative counts were fixed).
* Log fixed tags to NewRelic.
* Remove the ability to manually fix tag counts with the "Fix" button on
the /tags listing. This is no longer necessary now that tags are
fixed automatically.
Drop support for https://danbooru.donmai.us/cache/tags.json. This was a
nightly dump of the tags table that was originally added in #1012. It
was never documented and never really used except for by the DanbooruUp
extension.
Setting the statement timeout at the beginning didn't work because
`PostPruner.new.prune!` clobbers the timeout (it calls `without_timeout`,
which doesn't restore the timeout properly if the timeout was zero).
