Update frontend language tests for new keyboard shortcut convention

8af34a2295f2ff85cf0b introduced a failing test frontend test-
https://travis-ci.org/ether/etherpad-lite/builds/37931978

This commit updates both the German and English strings even though
the German locale files haven't been updated yet. The tests will
continue to fail but will stop as soon as translatewiki catches up.
Merge pull request #2272 from prtksxna/lang-tests

Update frontend language tests for new keyboard shortcut convention