update ci

.gitlab-ci.yml

@@ -5,9 +5,9 @@ stages:
 
 build:
   stage: build
-  image: ruby:2.5
+  image: ruby:2.6
   script:
-    - gem install bundler --no-ri --no-rdoc
+    - gem install bundler --no-document
     - bundle update
   artifacts:
     paths:
@@ -15,9 +15,9 @@ build:
 
 rubocop:
   stage: codequality
-  image: ruby:2.5
+  image: ruby:2.6
   script:
-    - gem install rubocop --no-ri --no-rdoc
+    - gem install rubocop rubocop-performance --no-document
     - rubocop
 
 dependency_scanning:

.rubocop.yml

@@ -1,3 +1,6 @@
+require:
+  - rubocop-performance
+
 AllCops:
   TargetRubyVersion: 2.3