build(deps): bump actions/cache from 3 to 4 (#311)

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci_docs.yml

@@ -36,7 +36,7 @@ jobs:
           python-version: 3.8
 
       - name: Cache pip
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ~/.cache/pip
           key: pip-${{ hashFiles('requirements.txt') }}-${{ hashFiles('_requirements/docs.txt') }}