github-actions(deps): bump actions/cache from 3 to 4

Bumps [actions/cache](https://github.com/actions/cache) from 3 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v3...v4)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/pnl-ci-docs.yml

@@ -92,7 +92,7 @@ jobs:
         echo "pip_cache_dir=$(python -m pip cache dir)" | tee -a $GITHUB_OUTPUT
 
     - name: Wheels cache
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ${{ steps.pip_cache.outputs.pip_cache_dir }}/wheels
         key: ${{ runner.os }}-python-${{ matrix.python-version }}-${{ matrix.python-architecture }}-pip-wheels-${{ hashFiles('requirements.txt', 'doc_requirements.txt') }}-${{ github.sha }}

.github/workflows/pnl-ci.yml

@@ -143,7 +143,7 @@ jobs:
         echo "pip_cache_dir=$(python -m pip cache dir)" | tee -a $GITHUB_OUTPUT
 
     - name: Wheels cache
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ${{ steps.pip_cache.outputs.pip_cache_dir }}/wheels
         key: ${{ runner.os }}-python-${{ matrix.python-version }}-${{ matrix.python-architecture }}-pip-wheels-${{ hashFiles('requirements.txt', 'dev_requirements.txt') }}-${{ github.sha }}