Remove $wgTitle from LanguageConverter subclasses

$wgTitle was simply used in these classes to prevent conversion
of prefixed names for files. Now that we have $wgNamespaceAliases
that is rendered moot, so this will instead return just the parent
class call for autoconvert().

Bug: 57562
Change-Id: I26f8a8aa0be3822056f286f2e15201cbe4d592bf
Merge "Remove $wgTitle from LanguageConverter subclasses"