Fix missing requires in specs

Adds missing require 'spec_helper' in some specs

spec/lib/gitlab/action_cable/request_store_callbacks_spec.rb

 # frozen_string_literal: true
 
+require 'spec_helper'
+
 RSpec.describe Gitlab::ActionCable::RequestStoreCallbacks do
   describe '.wrapper' do
     it 'enables RequestStore in the inner block' do

spec/lib/gitlab/database/load_balancing/action_cable_callbacks_spec.rb

 # frozen_string_literal: true
 
+require 'spec_helper'
+
 RSpec.describe Gitlab::Database::LoadBalancing::ActionCableCallbacks, :request_store do
   describe '.wrapper' do
     it 'uses primary and then releases the connection and clears the session' do