Use call in the adjustments recalculator's interface

We introduced an extension point for promotion adjustments in solidusio#4460 [1].

We change the expected interface from `#adjust!` to `#call` for
consistency, as that's the new standard we want to follow (see solidusio#4677 [2]
for an example). That's going to ease the adoption of a service layer if
we eventually introduce it.

[1] - solidusio#4460
[2] - solidusio#4677

core/app/models/spree/order_updater.rb

@@ -197,7 +197,7 @@ def log_state_change(name)
     end
 
     def update_promotions
-      Spree::Config.promotion_adjuster_class.new(order).adjust!
+      Spree::Config.promotion_adjuster_class.new(order).call
     end
 
     # DEPRECATED; this functionality is handled in #update_promotions

core/app/models/spree/promotion/order_adjustments_recalculator.rb

@@ -14,7 +14,7 @@ def initialize(order)
         @order = order
       end
 
-      def adjust!
+      def call
         all_items = line_items + shipments
         all_items.each do |item|
           promotion_adjustments = item.adjustments.select(&:promotion?)

core/spec/models/spree/promotion/order_adjustments_recalculator_spec.rb

@@ -3,9 +3,9 @@
 require 'rails_helper'
 
 RSpec.describe Spree::Promotion::OrderAdjustmentsRecalculator do
-  subject { described_class.new(order).adjust! }
+  subject { described_class.new(order).call }
 
-  describe '#adjust! ' do
+  describe '#call ' do
     describe 'promotion recalculation' do
       let(:order) { create(:order_with_line_items, line_items_count: 1, line_items_price: 10) }
       let(:line_item) { order.line_items[0] }