Fix easy rubocop issues

app/models/spree/adjustment.rb

@@ -128,7 +128,7 @@ module Spree
     end
 
     def display_amount
-      Spree::Money.new(amount, { currency: currency })
+      Spree::Money.new(amount, currency: currency)
     end
 
     def immutable?

app/models/spree/payment/processing.rb

@@ -179,11 +179,11 @@ module Spree
                     # For more information, please see Spree::Payment#set_unique_identifier
                     order_id: gateway_order_id }
 
-        options.merge!({ shipping: order.ship_total * 100,
-                         tax: order.tax_total * 100,
-                         subtotal: order.item_total * 100,
-                         discount: 0,
-                         currency: currency })
+        options.merge!(shipping: order.ship_total * 100,
+                       tax: order.tax_total * 100,
+                       subtotal: order.item_total * 100,
+                       discount: 0,
+                       currency: currency)
 
         options.merge!({ billing_address: order.bill_address.try(:active_merchant_hash),
                          shipping_address: order.ship_address.try(:active_merchant_hash) })

app/models/spree/tax_rate.rb

@@ -39,7 +39,7 @@ module Spree
       order.adjustments.tax.destroy_all
       order.line_item_adjustments.where(originator_type: 'Spree::TaxRate').destroy_all
 
-      self.match(order).each do |rate|
+      match(order).each do |rate|
         rate.adjust(order)
       end
     end