Bump actions/cache from 2 to 4 (#244)

Bumps [actions/cache](https://github.com/actions/cache) from 2 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v2...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/pr_validation.yml

@@ -69,7 +69,7 @@ jobs:
         with:
           dotnet-version: 8.0.*
       - name: Cache .nuke/temp, ~/.nuget/packages
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: |
             .nuke/temp