Remove WarmCacheService (#3527)

WarmCacheService is no longer used (removed with 5442083b ).

app/services/warm_cache_service.rb

-# frozen_string_literal: true
-
-class WarmCacheService < BaseService
-  def call(cacheable)
-    full_item = cacheable.class.where(id: cacheable.id).with_includes.first
-    Rails.cache.write(cacheable.cache_key, full_item)
-  end
-end