Fix Rubocop Failing Tests

[Droid00000]

Summary

Fixes these Rubocop offenses that are causing circle-ci tests to fail when making PR's.

xxxxxx@xxxxx discordrb % bundle exec rubocop
Inspecting 127 files
....................................................W.....................................W....................................

Offences:

lib/discordrb/data/overwrite.rb:68:7: W: Lint/Void: Literal false used in void context.
      false unless other.is_a? Discordrb::Overwrite
      ^^^^^
lib/discordrb/permissions.rb:139:7: W: Lint/Void: Literal false used in void context.
      false unless other.is_a? Discordrb::Permissions
      ^^^^^

Added

      # rubocop:disable Lint/Void
      false unless other.is_a? Discordrb::Permissions
      # rubocop:enable Lint/Void

Changed

Deprecated

Removed

Fixed

Rubocop offenses.