Bump actions/cache from 2 to 4

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]>

.github/workflows/template.yml

@@ -157,7 +157,7 @@ jobs:
 
       - name: Restore Package Cache
         if: runner.os != 'Windows' && steps.check-rmd.outputs.count != 0
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ${{ env.R_LIBS_USER }}
           key: ${{ runner.os }}-${{ hashFiles('.github/R-version') }}-1-${{ hashFiles('.github/depends.Rds') }}

.github/workflows/website.yml

@@ -55,7 +55,7 @@ jobs:
 
       - name: Restore R Cache
         if: steps.check-rmd.outputs.count != 0
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ${{ env.R_LIBS_USER }}
           key: ${{ runner.os }}-${{ hashFiles('.github/R-version') }}-1-${{ hashFiles('.github/depends.Rds') }}