NonDeterministicRequireOrder should also apply to require_relative

[gongfarmer]

This regards the cop Lint/NonDeterministicRequireOrder

Currently it does not flag code which uses require_relative instead of require, like this:

# require all ruby source files in ./update/
Dir.glob("#{__dir__}/update/*.rb") do |path|
  require_relative path
end

Current result:

$ rubocop lib/gpt/update.rb 
Inspecting 1 file
.

1 file inspected, no offenses detected

Desired result:

$ rubocop lib/gpt/update.rb 
Inspecting 1 file
W

Offenses:

lib/gpt/update.rb:6:1: W: [Correctable] Lint/NonDeterministicRequireOrder: Sort files before requiring them.
Dir.glob("#{__dir__}/update/*.rb") do |path|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

1 file inspected, 1 offense detected, 1 offense auto-correctable