Change auto-merge action to merge not rebase

Same goal achieved in keeping fork up to date but rebase doesn't display changes in Discord via bot post.

.github/workflows/auto-merge.yml

@@ -18,7 +18,7 @@ jobs:
         git config user.email "[email protected]" && git config user.name "Niam5"
         git remote add Cata https://github.com/The-Cataclysm-Preservation-Project/TrinityCore.git
         git fetch Cata master
-        git rebase Cata/master
+        git merge -m "Merge TheCataclysmPreservationProject to ElunaCataPreservation [skip ci]" Cata/master
         git status
     - name: Dependencies
       run: |