[CleanChanges] Set $wgCCTrailerFilter to true

Followup to Ib873d079d02c379bb027d028fc5b5f004fe43b54.
Second step: tweak to get the function as requested in the original
discussion and bug i.e. filter by language for translations etc.
Cf. <https://www.mediawiki.org/wiki/MediaWiki_Language_Extension_Bundle#Add.2Fupdate_your_LocalSettings.php>

If and when CleanChanges gets used by wikis without Translate,
this may need to be moved to InitialiseSettings.php.

Change-Id: Idaed2c73a7c7ee0cde9e16795a08f722a699ce7e