Revert GitHub Actions checkout action version to v6 (latest)

Author: DRSDavidSoft

.github/workflows/build.yml

@@ -35,7 +35,7 @@ jobs:
       discussions: write
     steps:
     - name: Check out repository code (Action from GitHub)
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0