.travis.yml in henkei-1.20.0 vs .travis.yml in henkei-1.21.0

@@ -2,13 +2,13 @@
   global:
     - CC_TEST_REPORTER_ID=bb96c1ff9dc66724c38fb4eb54486dd72dc88a7fd6e727c034b9cf8d747d069e
 
 language: ruby
 rvm:
-  - 2.2
   - 2.3
   - 2.4
   - 2.5
+  - 2.6
 
 before_install:
   - gem update bundler
 
 install: