Remove `FakeInformationSchema` override

Seems like the issue https://github.com/DatabaseCleaner/database_cleaner/issues/347
occurs only for MySQL. We removed support for MySQL in
https://gitlab.com/gitlab-org/gitlab-foss/merge_requests/29790.

spec/support/database_cleaner.rb

 # frozen_string_literal: true
 
-require 'database_cleaner/active_record/deletion'
 require_relative 'db_cleaner'
 
-module FakeInformationSchema
-  # Work around a bug in DatabaseCleaner when using the deletion strategy:
-  # https://github.com/DatabaseCleaner/database_cleaner/issues/347
-  #
-  # On MySQL, if the information schema is said to exist, we use an inaccurate
-  # row count leading to some tables not being cleaned when they should
-  def information_schema_exists?(_connection)
-    false
-  end
-end
-
-DatabaseCleaner::ActiveRecord::Deletion.prepend(FakeInformationSchema)
-
 RSpec.configure do |config|
   include DbCleaner