Pin runs-on image: ubuntu-latest -> ubuntu-22.04

Author: yasulab

.github/workflows/test.yml

@@ -53,7 +53,7 @@ jobs:
     if: github.ref == 'refs/heads/main'
     # TODO: This workflows depend on Ubuntu version.
     # https://github.com/AkhileshNS/heroku-deploy/issues/186
-    runs-on: ubuntu:22.04
+    runs-on: ubuntu-22.04
     steps:
       - uses: actions/checkout@v3
       - uses: akhileshns/heroku-deploy@v3.13.15