ci: bump actions/cache from 3 to 4 (#75)

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

Author: dependabot[bot]

.github/workflows/conda-dev.yml

@@ -43,7 +43,7 @@ jobs:
 
     - name: Cache conda
       id: cache
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       env:
         # Increase this value to reset cache if environment.devenv.yml has not changed
         CACHE_NUMBER: 1

.github/workflows/conda.yml

@@ -33,7 +33,7 @@ jobs:
           fetch-depth: 0
 
       - name: Cache conda
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ~/conda_pkgs_dir
           key: ${{matrix.os}}-conda-pkgs-${{hashFiles('**/conda/meta.yaml')}}