Updated mediawiki/extensions
Project: mediawiki/extensions/Translate  6bd39056ab407ce821e8be5162bb99956d313914
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Translation memory changes part 2

!! All message indexes need to be rebuild !!

Has some sprawling changes because I needed to fix failing tests.
Handle tm updating properly as described in
https://www.mediawiki.org/wiki/Help:Extension:Translate/Translation_memories#Solr_backend

* MessageGroups: fix cache clearing on group deletion
* MockFileBasedMessageGroup: above fixed exposed bugs here, which caused MessageGroupsTest to fail
* ApiQueryMessageTranslations: handle no results
* DatabaseTTMServer: cleanup unused code
* MessageIndex: added hook needed for ttmserver updating
* MessageIndex: in-process cache was not updated on store

Change-Id: I8ec094df0e4ebe7a997db6134f8926981a896224