Degrade Special:OrphanedTimedText gracefully if !$wgEnableLocalTimedText

When I was making the special page originally, I didn't realize it
was an option to disable the TimedText namespace. In such a case it
doesn't really make sense to have this special page listed.

Change-Id: I23e8fe3a6bf794e78e910c068d50ef10863c2fa4
Merge "Degrade Special:OrphanedTimedText gracefully if !$wgEnableLocalTimedText"