Deprecate other code related to old factories loading

People should have started to require testing_support/factory_bot
now, so this workaround is no longer needed.

Also no one is calling the methods that check for the version
of factory_bot, so we can safely deprecate that code.

core/lib/spree/testing_support.rb

@@ -1,6 +1,12 @@
 # frozen_string_literal: true
 
 require 'spree/testing_support/factory_bot'
+require 'spree/deprecation'
+
+Spree::Deprecation.warn <<-WARN
+  Using `require 'spree/testing_support'` is deprecated and will be removed in
+  Solidus 4.0.
+WARN
 
 module Spree
   module TestingSupport
@@ -11,5 +17,6 @@ module TestingSupport
     def check_factory_bot_version
       Spree::TestingSupport::FactoryBot.check_version
     end
+    deprecate :check_factory_bot_version, deprecator: Spree::Deprecation
   end
 end

core/lib/spree/testing_support/factory_bot.rb

@@ -30,6 +30,7 @@ def self.check_version
           MSG
         end
       end
+      deprecate :check_version, deprecator: Spree::Deprecation
 
       def self.add_definitions!
         ::FactoryBot.definition_file_paths.unshift(*definition_file_paths).uniq!