.travis.yml in async-rspec-1.13.0 vs .travis.yml in async-rspec-1.14.0

@@ -1,10 +1,9 @@
 language: ruby
 cache: bundler
 
 matrix:
   include:
-    - rvm: 2.3
     - rvm: 2.4
     - rvm: 2.5
     - rvm: 2.6
     - rvm: 2.6
       env: COVERAGE=BriefSummary,Coveralls