Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/deploy.yml

@@ -12,7 +12,7 @@ jobs:
     name: Build Docusaurus
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - uses: actions/setup-node@v4

.github/workflows/test-deploy.yml

@@ -12,7 +12,7 @@ jobs:
     name: Test deployment
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - uses: actions/setup-node@v4