Update test matrix for ruby 4.0

Author: aelkiss

.github/workflows/tests.yml

@@ -8,9 +8,9 @@ jobs:
     name: Ruby ${{ matrix.ruby }}
     strategy:
       matrix:
-        ruby: [2.7, 3.0, 3.1, 3.2]
+        ruby: [3.0, 3.1, 3.2, 4.0]
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v6
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with: