Stop faking custom URLs for controllers classes with exactly two consecutive uppercas...

Stop faking custom URLs for controllers classes with exactly two consecutive uppercase characters

This was introduced in 519f15c7700222357952e8cab41bbe960730c7fd and its purpose
is not entirely clear: Everything works identically even without this, even in
WoltLab Suite 5.5.

RoutingCacheBuilder is only ever used within ControllerMap and within
ControllerMap there are just a few locations where custom URLs are processed:

- resolve(): This enforces that renamed controllers are accessed via their
  canonical URL. Not relevant here, because we are already working with the
  canonical URL and it's not an intentional rename.
- resolveCustomController(): This is what we intent to avoid. If this method
  does not match, then `->resolve()` will correctly match.
- lookup(): `self::transformController()` will perform the correct
  transformation.
- lookupCmsPage(): Not relevant, because we do not deal with CMS pages.