The language module should flush l10n caches after translation
update, otherwise translation changes have no immediate effect.

Change-Id: Ibf412293139e6fc82da243ba22d7d13d187add5e
Resolves: #75778
Releases: master, 7.6
Reviewed-on: https://review.typo3.org/47780


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>