chore(deps): update actions/cache action to v6 (#304)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/tests.yml

@@ -36,7 +36,7 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Cache Homebrew Bundler RubyGems
-        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae  # v5.0.5
+        uses: actions/cache@2c8a9bd7457de244a408f35966fab2fb45fda9c8  # v6.0.0
         with:
           path: ${{ steps.set-up-homebrew.outputs.gems-path }}
           key: ubuntu-latest-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}
@@ -338,7 +338,7 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Cache Homebrew Bundler RubyGems
-        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae  # v5.0.5
+        uses: actions/cache@2c8a9bd7457de244a408f35966fab2fb45fda9c8  # v6.0.0
         with:
           path: ${{ steps.set-up-homebrew.outputs.gems-path }}
           key: ${{ matrix.os }}-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}