Remove register method from Calculator

[nishant-cyro]

We are not using this method anymore. Now, we use to register calculators like this -

config = Rails.application.config
config.spree.calculators.tax_rates << CustomCalculator
config.spree.calculators.shipping_methods << CustomCalculator
config.spree.calculators.promotion_actions_create_adjustments << CustomCalculator

[Mafi88]

It seems to be unused both in code and according to https://github.com/spree/spree/blob/master/guides/content/developer/core/calculators.md.

However, shipment guide still mentions it as an example: https://github.com/spree/spree/blob/master/guides/content/developer/core/shipments.md#default-calculators.
And won't it brake existing extensions?

@nishant-cyro @priyank-gupta @damianlegawiec Any thoughts about it?

[nishant-cyro]

@Mafi88 - Even if register method is there, it is not doing anything, so the extensions won't be working as expected.

Also, as mentioned in the guides for spree_active_shipping is outdated as spree_active_shipping is not using it too. https://github.com/spree/spree/blob/master/guides/content/developer/core/shipments.md#default-calculators

[Mafi88]

👍