.github: bump peter-evans/create-pull-request from 8.0.0 to 8.1.0

Bumps [peter-evans/create-pull-request](https://github.com/peter-evans/create-pull-request) from 8.0.0 to 8.1.0.
- [Release notes](https://github.com/peter-evans/create-pull-request/releases)
- [Commits](https://github.com/peter-evans/create-pull-request/compare/98357b18bf14b5342f975ff684046ec3b2a07725...c0f553fe549906ede9cf27b5156039d195d2ece0)

---
updated-dependencies:
- dependency-name: peter-evans/create-pull-request
  dependency-version: 8.1.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/update-flake.yml

@@ -35,7 +35,7 @@ jobs:
           private-key: ${{ secrets.CODE_UPDATER_APP_PRIVATE_KEY }}
 
       - name: Send pull request
-        uses: peter-evans/create-pull-request@98357b18bf14b5342f975ff684046ec3b2a07725 #v8.0.0
+        uses: peter-evans/create-pull-request@c0f553fe549906ede9cf27b5156039d195d2ece0 #v8.1.0
         with:
           token: ${{ steps.generate-token.outputs.token }}
           author: Flakes Updater <noreply+flakes-updater@tailscale.com>