chore(deps): update actions/checkout action to v6

.gitea/workflows/ci.yaml

@@ -10,7 +10,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
         with:
           go-version: 'stable'
@@ -20,7 +20,7 @@ jobs:
   vulnerabilities:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
         with:
           go-version: 'stable'