Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v5
         with:
           node-version: '20.x'

.github/workflows/release.yml

@@ -13,7 +13,7 @@ jobs:
       pull-requests: write
       id-token: write
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v5
         with:
           node-version: 20