Translation keys still in the code deleted

[YohYamasaki]

The following translation keys have been removed from Phrase but are still in the code, so we need to manually add the keys to the en.ts, de.ts and die_sie.ts files to pass the test.
These keys are in the code, but as the local admin group is deprecated, their use should be removed from the code.

"localAdminGroup_label": "Local admin group",
"assignAdminRightsToLocallyAdministratedUserError_msg": "You can't assign global admin rights to a locally administrated user.",
"localAdminGroups_label": "Local admin groups"

Tasks

• Remove all the places which uses the above keys in the code.

[charlag]

see #8137