remove bundler cache to debug build

remove bundler cache to debug build

diff --git a/.travis.yml b/.travis.yml
index 7bca664..d1781da 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,12 +24,10 @@ matrix:
     - rvm: 2.6
       gemfile: gemfiles/rails_master.gemfile
 
-cache: bundler
-
 sudo: false
 
 install: bundle install --without development --retry=3 --jobs=3
 
 script:
   - bundle exec rubocop
-  - RACK_ENV=test RAILS_ENV=test bundle exec rspec
+  - bundle exec rspec

GitHub sha: e28ce66a