infra: Upgrade GitHub actions actions/checkout to v4

v2 of actions/checkout uses deprecated dependencies.

Signed-off-by: Rahul Rameshbabu <[email protected]>

Author: Binary-Eater

.github/workflows/gh-pages.yml

@@ -10,7 +10,7 @@ jobs:
   deploy:
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           submodules: true  # Fetch Hugo themes (true OR recursive)
           fetch-depth: 0    # Fetch all history for .GitInfo and .Lastmod