Update checkout action version to 4

Author: styd

.github/workflows/build-test.yml

@@ -17,7 +17,7 @@ jobs:
         ruby: [2.6, 2.7, '3.0', 3.1, 3.2, 3.3]
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with: