Merge pull request #50 from googlefonts/renovate/actions-cache-4.x

Update actions/cache action to v4

.github/workflows/main.yml

@@ -18,7 +18,7 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
 
-    - uses: actions/cache@v2
+    - uses: actions/cache@v4
       with:
         path: .venv
         key: ${{ runner.os }}-poetry-${{ hashFiles('poetry.lock') }}