Update versions of actions used in deploy workflow.

Author: Zimmi48

.github/workflows/deploy_heroku.yml

@@ -9,10 +9,10 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Build release Docker image
         run: docker build -f release.Dockerfile . -t coqbot
-      - uses: akhileshns/heroku-deploy@v3.12.14
+      - uses: akhileshns/heroku-deploy@v3.13.15
         with:
           heroku_api_key: ${{secrets.HEROKU_API_KEY}}
           heroku_app_name: coqbot