Drop unsupported Ruby version

PowerKiKi · PowerKiKi · commit 6a35bbad882f · 2020-05-27T09:54:11.000+09:00
Ruby 2.7 is not yet supported by Redmine: https://www.redmine.org/issues/31500
diff --git a/.rubocop.yml b/.rubocop.yml
@@ -6,7 +6,7 @@ Rails:
   Enabled: true
 
 AllCops:
-  TargetRubyVersion: 2.3
+  TargetRubyVersion: 2.5
   TargetRailsVersion: 5.2
   Include:
     - '**/*.ruby'
diff --git a/.travis.yml b/.travis.yml
@@ -2,9 +2,8 @@ language: ruby
 sudo: required
 cache: bundler
 rvm:
-  - 2.6.3
-  - 2.4.6
-  - 2.3.8
+  - 2.6
+  - 2.5
 gemfile:
   - Gemfile
 services:
