chore(deps): update actions/cache action to v4

Author: renovate-bot

.github/workflows/tests.yml

@@ -31,7 +31,7 @@ jobs:
 
       - uses: Gr1N/setup-poetry@v4
 
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: ~/.cache/pypoetry/virtualenvs
           key: ${{ matrix.os }}-${{ matrix.python-version }}-poetry-${{ hashFiles('pyproject.toml') }}