ci: install ffmpeg only if linting succeeds

.github/workflows/ci.yml

@@ -14,10 +14,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - name: Install ffmpeg
-      run: |
-        sudo apt update
-        sudo apt install -yq --no-install-recommends ffmpeg
     - name: Set up Python
       uses: actions/setup-python@v4
       with:
@@ -34,6 +30,10 @@ jobs:
     - name: Type check
       if: '!cancelled()'
       run: mypy
+    - name: Install ffmpeg
+      run: |
+        sudo apt update
+        sudo apt install -yq --no-install-recommends ffmpeg
     - name: Test
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}