Update actions/checkout action to v4.2.1

.github/workflows/testing.yml

@@ -43,7 +43,7 @@ jobs:
           go-version: ${{ matrix.go }}
 
       - name: Check out code into the Go module directory
-        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+        uses: actions/checkout@eef61447b9ff4aafe5dcd4e0bbf5d482be7e7871 # v4.2.1
         with:
           persist-credentials: false
           fetch-depth: 0