sudo: false
language: ruby
rvm:
  - 2.0.0
  - 2.1.10
  - 2.2.10
  - 2.3.8
  - 2.4.7
  - 2.5.6
  - 2.6.4
  - ruby-head
before_install:
  - |
    if [[ `ruby -v` =~ 2\.[0-2]\.[0-9]+ ]]; then
      gem install rubygems-update -v '<3' && update_rubygems
      gem install bundler -v '<2'
    else
      gem update --system
      gem update bundler
    fi

language: ruby
rvm:
  - 2.0.0
  - 2.1.10
  - 2.2.10
  - 2.3.8
  - 2.4.7
  - 2.5.6
  - 2.6.4
  - ruby-head
before_install:
  - |
    if [[ `ruby -v` =~ 2\.[0-2]\.[0-9]+ ]]; then
      gem install rubygems-update -v '<3' && update_rubygems
      gem install bundler -v '<2'
    else
      gem update --system
      gem update bundler
    fi

Remove unused `sudo: false` in Travis CI settings
Remove unused `sudo: false` in Travis CI settings

`sudo: false` has been phased out.
Now the virtual-machine-based Linux is always used.
See: https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration
