language: ruby

rvm:
  - 2.2.10
  - 2.3.8
  - 2.4.10
  - 2.5.8
  - 2.6.6
  - 2.7.1

before_install: gem install bundler --no-document

language: ruby

rvm:
  - 2.2.10
  - 2.3.8
  - 2.4.10
  - 2.5.8
  - 2.6.6
  - 2.7.1

Remove unnecessary step to fix CI
Remove unnecessary step to fix CI

It seems bundler is installed by travis without any setting

https://travis-ci.org/github/yuya-takeyama/flagship/jobs/678123423

```
$ gem install bundler --no-document
ERROR:  Error installing bundler:
	bundler requires Ruby version >= 2.3.0.
The command "gem install bundler --no-document" failed and exited with 1 during .
```
