Install Firefox manually in test setup steps

Firefox isn't installed in ubuntu-latest anymore.

.github/workflows/test.yaml

@@ -12,6 +12,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+      - name: Install Firefox
+        run: sudo snap remove firefox && sudo add-apt-repository ppa:mozillateam/ppa && sudo apt install --target-release 'o=LP-PPA-mozillateam' firefox
       - uses: browser-actions/setup-geckodriver@latest
       - name: Install poetry
         run: pipx install poetry==1.1.15