Remove monkey patch for doorkeeper 4.x versions

Doorkeeper has been upgraded to 5.0.2 which already includes the class
that was being monkey patched into this initializer. Remove the monkey
patch so that we can leverage the functionality in doorkeeper instsead.

config/initializers/doorkeeper.rb

@@ -113,53 +113,3 @@ Doorkeeper.configure do
 
   base_controller '::Gitlab::BaseDoorkeeperController'
 end
-
-# Monkey patch to avoid creating new applications if the scope of the
-# app created does not match the complete list of scopes of the configured app.
-# It also prevents the OAuth authorize application window to appear every time.
-
-# Remove after we upgrade the doorkeeper gem from version 4.x
-if Doorkeeper.gem_version > Gem::Version.new('5.0.0')
-  raise "Doorkeeper was upgraded, please remove the monkey patch in #{__FILE__}"
-end
-
-module Doorkeeper
-  module AccessTokenMixin
-    module ClassMethods
-      def matching_token_for(application, resource_owner_or_id, scopes)
-        resource_owner_id =
-          if resource_owner_or_id.respond_to?(:to_key)
-            resource_owner_or_id.id
-          else
-            resource_owner_or_id
-          end
-
-        tokens = authorized_tokens_for(application.try(:id), resource_owner_id)
-        tokens.detect do |token|
-          scopes_match?(token.scopes, scopes, application.try(:scopes))
-        end
-      end
-
-      def scopes_match?(token_scopes, param_scopes, app_scopes)
-        return true if token_scopes.empty? && param_scopes.empty?
-
-        (token_scopes.sort == param_scopes.sort) &&
-          Doorkeeper::OAuth::Helpers::ScopeChecker.valid?(
-            param_scopes.to_s,
-            Doorkeeper.configuration.scopes,
-            app_scopes)
-      end
-
-      def authorized_tokens_for(application_id, resource_owner_id)
-        ordered_by(:created_at, :desc)
-          .where(application_id: application_id,
-                 resource_owner_id: resource_owner_id,
-                 revoked_at: nil)
-      end
-
-      def last_authorized_token_for(application_id, resource_owner_id)
-        authorized_tokens_for(application_id, resource_owner_id).first
-      end
-    end
-  end
-end