ci(github): update the checkout action to v4

Author: Linkid

.github/workflows/deploy.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Get themes
         run: |