ci: fix grammar issue (#1626)

.github/workflows/build.yml

@@ -3,8 +3,6 @@ name: Build & Test
 on:
   pull_request_target:
     branches: [master]
-  pull_request_target:
-    branches: [master]
 
 # Cancels all previous workflow runs for pull requests that have not completed.
 # See https://docs.github.com/en/actions/using-jobs/using-concurrency