chore: update the workflow of "Check pull request target"

.github/workflows/pull-request.yml

@@ -1,17 +1,19 @@
 name: Check pull request target
 on:
-  pull_request_target:
+  pull_request:
     types:
       - opened
       - reopened
       - synchronize
+    branches:
+      - master
 jobs:
   check-branches:
     runs-on: ubuntu-latest
     steps:
       - name: Check target branch
         run: |
-          if [ ${{ github.base_ref }} == "master" ] && [ ${{ github.head_ref }} != "dev" ]; then
+          if [ ${{ github.head_ref }} != "dev" ]; then
             echo "Only pull requests from dev branch are only allowed to be merged into master branch."
             exit 1
-          fi
+          fi