Change CODEOWNER for strings to UA team (#1828)

This way only one person of the team has to approve and adding/removing UA team members doesn't require changes to the CODEOWNERS file.

Co-authored-by: Ralf Gehrer <ralfgehrer@users.noreply.github.com>

CODEOWNERS

@@ -8,4 +8,4 @@
 * @corona-warn-app/cwa-app-android-maintainers
 
 # Code Onwer of all german texts
-/Corona-Warn-App/src/main/res/values-de/ @janetback @SabineLoss
+/Corona-Warn-App/src/main/res/values-de/ @corona-warn-app/cwa-app-android-ua