CI Deploy preview environmentの不要なトリガー削除 (#9558)

* CI Deploy preview environmentの不要なトリガー削除

* 不要な条件削除

.github/workflows/pr-preview-deploy.yml

@@ -1,7 +1,5 @@
 # Run secret-dependent integration tests only after /deploy approval
 on:
-  pull_request:
-    types: [opened, reopened, synchronize]
   repository_dispatch:
     types: [deploy-command]
 
@@ -12,7 +10,6 @@ jobs:
   deploy-preview-environment:
     runs-on: ubuntu-latest
     if:
-      github.event_name == 'repository_dispatch' &&
       github.event.client_payload.slash_command.sha != '' &&
       contains(github.event.client_payload.pull_request.head.sha, github.event.client_payload.slash_command.sha)
     steps: