Live-Search uses hardcoded texts
The labels within the livesearch fly-out are not internationalized but hardcoded within $helpContent (class.extdirect_dataprovider_backendlivesearch):
These texts are
- "How to use advanced search tags" and
- "Search in certain tables: page:Home will search for all pages with the title "Home""
Put labels into 'LANG'
(issue imported from #M16481)