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

Author: renovate[bot]

.github/workflows/django-ci.yml

@@ -44,7 +44,7 @@ jobs:
           python-version: '3.13.1'
 
       - name: Cache Poetry dependencies
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ~/.cache/pypoetry
           key: ${{ runner.os }}-poetry-${{ hashFiles('**/poetry.lock') }}