In memory sort of variant.options_text

Assume that the option_values -> option_types have been eager loaded via joins/includes and simply sort in memory. Removing the explicit query removes N queries for products/show in the api where N = number of variants that belong to the product. This should allow us to fully take advantage of the API optimization made here:

https://github.com/spree/spree/commit/30597b2aa7a1f47b5e636750baf7c100f0cc42b2

Fixes #4294
remove rspec deprecated stub