chore(deps): Bump 8398a7/action-slack from 3.8.3 to 3.15.0

Bumps [8398a7/action-slack](https://github.com/8398a7/action-slack) from 3.8.3 to 3.15.0.
- [Release notes](https://github.com/8398a7/action-slack/releases)
- [Commits](8398a7/action-slack@fac0d8d...bdc6f9d)

---
updated-dependencies:
- dependency-name: 8398a7/action-slack
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/ci.yml

@@ -36,7 +36,7 @@ jobs:
         name: Report code coverage
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
-      - uses: 8398a7/action-slack@fac0d8dcd9eec18c79dae8addc99aab092c4cc50
+      - uses: 8398a7/action-slack@bdc6f9de222d3b7518e6cf99c4f3410f653cfde3
         name: Notify on Slack
         if: always() # Pick up events even if the job fails or is canceled.
         with: