Revert "ci/contrib: do not fail on missing gh-pages"

Author: weihanglo

.github/workflows/contrib.yml

@@ -29,12 +29,14 @@ jobs:
       run: |
         cd src/doc/contrib
         mdbook build
-        # Override previous ref to avoid keeping history.
-        git worktree add --orphan -B gh-pages gh-pages
+        git worktree add gh-pages gh-pages
         git config user.name "Deploy from CI"
         git config user.email ""
         cd gh-pages
+        # Delete the ref to avoid keeping history.
+        git update-ref -d refs/heads/gh-pages
+        rm -rf contrib
         mv ../book contrib
         git add contrib
         git commit -m "Deploy $GITHUB_SHA to gh-pages"
-        git push origin +gh-pages
+        git push --force