Fixed RuboCop offense Style/ClassAndModuleChildren

$ bundle exec rubocop
Inspecting 11 files
..........C

Offenses:

spec/support/request_helpers.rb:1:8: C: Use nested module/class
definitions instead of compact style.
module MediawikiApi::RequestHelpers
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

11 files inspected, 1 offense detected

Bug: 63307
Change-Id: Id4858bf4402526563757aaa7a3257e68918487f2