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

Author: renovate[bot]

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
       matrix:
         go-version: [1.24.x]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-go@v5
         with:
           go-version: ${{ matrix.go-version }}
@@ -18,7 +18,7 @@ jobs:
     name: tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-go@v5
         with:
           go-version: 1.24