ci: drop --delete-branch from reconcile auto-merge call (#6534)

The reconcile job runs without a git checkout, so gh pr merge --delete-branch
fails with 'not a git repository' before enabling auto-merge. Auto-merge
itself needs no local git state; branch cleanup is already handled by the
PR-creating workflows.

.github/workflows/bot-auto-merge-reconcile.yml

@@ -36,5 +36,5 @@ jobs:
             --jq '.[] | select(.author.login as $login | ["app/homarr-renovate", "app/homarr-crowdin", "app/homarr-update-contributors", "app/homarr-releases"] | index($login)) | select(.reviewDecision == "APPROVED") | select(.mergeStateStatus == "CLEAN") | select(.autoMergeRequest == null) | .number' \
           | while read -r pr; do
               echo "Re-enabling auto-merge on PR #$pr"
-              gh pr merge "$pr" --auto --squash --delete-branch
+              gh pr merge "$pr" --auto --squash
             done