Bump actions/cache from 4 to 5

Bumps [actions/cache](https://github.com/actions/cache) from 4 to 5.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v4...v5)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ExportPluto.yml

@@ -35,7 +35,7 @@ jobs:
       # We set up a folder that Pluto can use to cache exported notebooks. If the notebook file did not change,
       # then Pluto can take the exported file from cache instead of running the notebook.
       - name: Set up notebook state cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: pluto_state_cache
           key: ${{ runner.os }}-pluto_state_cache-v2-${{ hashFiles('**/Project.toml', '**/Manifest.toml', '.github/workflows/*' ) }}-${{ hashFiles('**/*jl') }}