Bump cirrus-actions/rebase from 1.5 to 1.8

Bumps [cirrus-actions/rebase](https://github.com/cirrus-actions/rebase) from 1.5 to 1.8.
- [Release notes](https://github.com/cirrus-actions/rebase/releases)
- [Commits](cirrus-actions/rebase@1.5...1.8)

---
updated-dependencies:
- dependency-name: cirrus-actions/rebase
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/rebase.yml

@@ -16,6 +16,6 @@ jobs:
           token: ${{ secrets.ACTIONS_TOKEN }}
           fetch-depth: 0 # otherwise, you will fail to push refs to dest repo
       - name: Automatic Rebase
-        uses: cirrus-actions/rebase@1.5
+        uses: cirrus-actions/rebase@1.8
         env:
           GITHUB_TOKEN: ${{ secrets.ACTIONS_TOKEN }}