bump actions/cache

Author: joelhawksley

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: 3.4.3
-    - uses: actions/cache@v2
+    - uses: actions/cache@v4
       with:
         path: vendor/bundle
         key: gems-${{ hashFiles('**/Gemfile.lock') }}