Bump AkhileshNS/heroku-deploy from 3.13.15 to 4

Bumps [AkhileshNS/heroku-deploy](https://github.com/akhileshns/heroku-deploy) from 3.13.15 to 4.
- [Release notes](https://github.com/akhileshns/heroku-deploy/releases)
- [Commits](AkhileshNS/heroku-deploy@v3.13.15...v4)

---
updated-dependencies:
- dependency-name: AkhileshNS/heroku-deploy
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/deploy_heroku.yml

@@ -25,7 +25,7 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-gradle-
       - name: Deploy to Heroku
-        uses: AkhileshNS/heroku-deploy@v3.13.15
+        uses: AkhileshNS/heroku-deploy@v4
         with:
           heroku_api_key: ${{secrets.HEROKU_API_KEY}}
           heroku_app_name: http4k-irc