Delete un-used file

The method
run_with_new_database_connection
does not seem used anymore

spec/services/groups/destroy_service_spec.rb

@@ -3,8 +3,6 @@
 require 'spec_helper'
 
 RSpec.describe Groups::DestroyService do
-  include DatabaseConnectionHelpers
-
   let!(:user)         { create(:user) }
   let!(:group)        { create(:group) }
   let!(:nested_group) { create(:group, parent: group) }

spec/support/helpers/database_connection_helpers.rb

-# frozen_string_literal: true
-
-module DatabaseConnectionHelpers
-  def run_with_new_database_connection
-    pool = ActiveRecord::Base.connection_pool
-    conn = pool.checkout
-    yield conn
-  ensure
-    pool.checkin(conn)
-  end
-end