Update build.yml - update build-action version.

Author: josteink

.github/workflows/build.yml

@@ -28,7 +28,7 @@ jobs:
 
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - uses: jcs090218/setup-emacs@master
         with: