Sort pages in categories without namespace prefix

Sort pages in categories without namespace prefix

This removes $wgCategoryPrefixedDefaultSortkey and effectively always
makes it false.  The setting was added in the first place to hack around
the default, clearly broken behavior, but this just fixes it instead, so
the setting is no longer needed.

Running maintenance/updateCollation.php for the first time will fix
this, no need to run refreshLinks.php.  If you've already run
updateCollation.php, you can do UPDATE categorylinks SET cl_collation =
76; or such and then run the script again.