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/ci.yaml

@@ -46,7 +46,7 @@ jobs:
           CONDA_PREFIX=$(python -c "import sys; print(sys.prefix)")
           echo "CONDA_PREFIX=$CONDA_PREFIX" >> $GITHUB_ENV
 
-      - uses: actions/cache@v3
+      - uses: actions/cache@v4
         with:
           path: ${{ env.CONDA_PREFIX }}
           key: ${{ matrix.os }}-${{matrix.python-version}}-conda-${{ hashFiles('continuous_integration/environment.yaml') }}-${{ env.DATE }}-${{matrix.experimental}}-${{ env.CACHE_NUMBER }}