chore(deps): update actions/cache action to v6

Author: renovate[bot]

.github/workflows/tests.yml

@@ -17,7 +17,7 @@ jobs:
 
       - name: Cache Homebrew Bundler RubyGems
         id: cache
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: ${{ steps.set-up-homebrew.outputs.gems-path }}
           key: ${{ runner.os }}-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}