chore(deps): update actions/checkout action to v4

.github/workflows/pull_request.yml

@@ -25,7 +25,7 @@ jobs:
 
       # https://github.com/marketplace/actions/checkout
       - name: Check out code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           path: go/src/github.com/${{ github.repository }}
           fetch-depth: 0