Update actions/cache action to v4 (#1847)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/actions/run_tests/action.yaml

@@ -21,7 +21,7 @@ runs:
     shell: bash
 
   - name: poetry cache # Change CACHE_STRING secret to bust the cache
-    uses: actions/cache@v3
+    uses: actions/cache@v4
     with:
       path: .venv
       key: ${{ runner.os }}-${{ hashFiles('poetry.lock') }}-${{ env.PYTHON_FULL_VERSION }}-${{ inputs.cache-string }}

.github/workflows/docs.yaml

@@ -50,13 +50,13 @@ jobs:
       run: echo "PYTHON_FULL_VERSION=$(python --version)" >> "$GITHUB_ENV"
 
     - name: poetry cache
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: .venv
         key: ${{ runner.os }}-${{ hashFiles('poetry.lock') }}-${{ env.PYTHON_FULL_VERSION }}-${{ secrets.CACHE_STRING }}
 
     - name: npm cache
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: node_modules
         key: ${{ runner.os }}-pa11y-v3