Bump actions/cache from 5.0.5 to 6.1.0

Bumps [actions/cache](https://github.com/actions/cache) from 5.0.5 to 6.1.0.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v5.0.5...v6.1.0)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -39,7 +39,7 @@ jobs:
         run: echo "date=$(date +'%Y-%m-%d')" >> $GITHUB_OUTPUT
 
       - name: 'Setup data cache'
-        uses: actions/cache@v5.0.5
+        uses: actions/cache@v6.1.0
         with:
           path: src/.observablehq/cache
           key: data-${{ hashFiles('src/data/*') }}-${{ steps.date.outputs.date }}