Update pull_request.yml

.github/workflows/pull_request.yml

@@ -1,24 +1,20 @@
 name: CI/Rubocop
 
-on:
-  pull_request:
-    branches:
-      - master
+on: [push, pull_request]
 
 jobs:
   build:
-
     runs-on: ubuntu-latest
-
     steps:
-    - uses: actions/checkout@v1
-    - name: Set up Ruby 2.6
+    - uses: actions/checkout@master
+    - name: Setup Ruby
       uses: actions/setup-ruby@v1
       with:
         ruby-version: 2.6.x
     - name: Build and test with Rake/Rubocop
       run: |
-        gem install bundler
+        gem install bundler:1.14.0
+        bundle update
         bundle install --jobs 4 --retry 3
-        bundle exec rake test
+        bundle exec rake
         bundle exec rubocop --display-cop-names