Update build-doc.yml

Signed-off-by: Yang Pan <[email protected]>

Author: yangpanMS

.github/workflows/build-doc.yml

@@ -1,11 +1,8 @@
 name: PR build check for Docusaurus site
 
 on:
-  push:
-    branches:
-      - main
-    # Review gh actions docs if you want to further define triggers, paths, etc
-    # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#on
+  pull_request:
+    branches: [ "main" ]
 
 defaults:
   run:
@@ -28,4 +25,4 @@ jobs:
         run: yarn install --frozen-lockfile
 
       - name: Build website
-        run: yarn build
+        run: yarn build