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] <[email protected]>

Author: dependabot[bot]

.github/workflows/dart.yml

@@ -19,7 +19,7 @@ jobs:
     name: "Dart CI"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: "~/.pub-cache/hosted"
           key: "os:ubuntu-latest;pub-cache-hosted;dart:stable"