ci: bump actions/create-github-app-token from 2 to 3

Bumps [actions/create-github-app-token](https://github.com/actions/create-github-app-token) from 2 to 3.
- [Release notes](https://github.com/actions/create-github-app-token/releases)
- [Commits](https://github.com/actions/create-github-app-token/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/create-github-app-token
  dependency-version: '3'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/update-flake.yml

@@ -14,7 +14,7 @@ jobs:
         branch: [master, release-25.11]
     steps:
       - name: Create GitHub App token
-        uses: actions/create-github-app-token@v2
+        uses: actions/create-github-app-token@v3
         if: vars.CI_APP_ID
         id: app-token
         with: