Update GitHub Actions

Author: okuramasafumi

.github/workflows/main.yml

@@ -8,10 +8,10 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        ruby: [2.5, 2.6, 2.7, 3.0, head]
+        ruby: [2.5, 2.6, 2.7, '3.0', 3.1, 3.2, 3.3 head]
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with: