Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/update.yml

@@ -9,7 +9,7 @@ jobs:
   update:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Set up Go
       uses: actions/setup-go@v3