gh actions: switch actions/checkout version to main

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
     # NOTE: odin macos and ubuntu releases are zipped twice, so this is bit of a hack.
     # The examples folder also conflicts with the sokol examples, so we just remove it.
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: ilammy/msvc-dev-cmd@v1
       - if: runner.os == 'Linux'
         name: prepare-linux