Source code (Git repository) shouldn’t contain .qm files

[hpreusse]

This is similar to #798.

When looking into the trans/qt folder one notices that there are a lot of pre-generated qm files, which are sitting in the repository. These files should be removed and generated from the ts files during build using /usr/lib/qt6/bin/lrelease as it is done for the TeXworks...ts files. Many thanks!