Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/deploy-docs.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           # if your docs needs submodules, uncomment the following line