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

Author: renovate[bot]

.github/workflows/deploy-docs.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v5