ci: update backport bot templates (#2821)

### Description

Better integrations with release-please, using my action fork until
https://github.com/tibdex/backport/pull/109 is merged upstream.

.github/workflows/backport.yml

@@ -22,6 +22,13 @@ jobs:
         )
       )
     steps:
-      - uses: tibdex/backport@v2
+      - uses: jooola/backport@main
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
+          title_template: <%= title %> (<%= base %>)
+          body_template: |
+            Backport <%= mergeCommitSha %> from #<%= number %>.
+
+            BEGIN_COMMIT_OVERRIDE
+            <%= title %>
+            END_COMMIT_OVERRIDE