Bump julia-actions/cache from 1 to 2

Bumps [julia-actions/cache](https://github.com/julia-actions/cache) from 1 to 2.
- [Release notes](https://github.com/julia-actions/cache/releases)
- [Changelog](https://github.com/julia-actions/cache/blob/main/devdocs/making_a_new_release.md)
- [Commits](julia-actions/cache@v1...v2)

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

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

.github/workflows/documentation.yml

@@ -19,7 +19,7 @@ jobs:
       - uses: julia-actions/setup-julia@v2
         with:
           version: '1.6'
-      - uses: julia-actions/cache@v1
+      - uses: julia-actions/cache@v2
       - name: Install dependencies
         run: julia --project=docs/ -e 'using Pkg; Pkg.add("Documenter"); Pkg.develop("./"); Pkg.instantiate()'
       - name: Build and deploy