Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/ci.yaml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: '18.20.8'
@@ -24,7 +24,7 @@ jobs:
     needs: setup
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: '18.20.8'
@@ -46,7 +46,7 @@ jobs:
         node: ['18', '20']
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node }}

.github/workflows/gh-pages.yml

@@ -22,7 +22,7 @@ jobs:
       run:
         working-directory: website
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: 18.20.8