fix: existing pr check using wrong token

Author: HDVinnie

.github/workflows/database-schema.yml

@@ -116,7 +116,7 @@ jobs:
             echo "existing_pr=false" >> $GITHUB_OUTPUT
           fi
         env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_TOKEN: ${{ secrets.PERSONAL_ACCESS_TOKEN }}
 
       - name: Update existing PR branch
         if: steps.diff.outputs.has_changes == 'true' && steps.check-pr.outputs.existing_pr == 'true'