Update actions/checkout action to v3

Author: renovate-bot

.github/workflows/docusaurus.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - name: Check out repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       # Node is required for npm
       - name: Set up Node
         uses: actions/setup-node@v2