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

Author: renovate-rancher[bot]

.github/workflows/unitest.yaml

@@ -8,7 +8,7 @@ jobs:
   unitest:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: actions/setup-go@v5
       with:
         go-version: '1.22.3'