Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/go.yml

@@ -14,7 +14,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
 
     - name: Set up Go
       uses: actions/setup-go@v4

.github/workflows/release.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     permissions: write-all
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v6
     # https://github.com/wangyoucao577/go-release-action
 
     - name: Set version variable