Update ruby

.trustie-pipeline.yml

@@ -8,16 +8,14 @@ platform:
 
 steps:
 - name: install
-  image: ruby:2.3.7
+  image: ruby:2.4.5
   commands:
-  - gem update --system
-  - gem install bundler --default -v "2.1.4"
   - bundle -v
-  - bundle _2.1.4_ install --jobs=1 --retry=1
+  - bundle  install --jobs=1 --retry=1
   - rake
 
 - name: test
-  image: ruby:2.3.7
+  image: ruby:2.4.5
   volumes:
   - name: bundle
     path: /usr/local/bundle