Fix failing spec since Solidus address format change

Because of addresses' firstname & lastname deprecations in solidusio/solidus#3584,
solidusio/solidus#3524 and probably other PRs, the inputs where deleted
in favor of a single `name` input.
This is only on master for now, so it should be in 2.11 or 3.0.

spec/features/checkout_spec.rb

@@ -147,8 +147,14 @@
 
   def fill_in_address
     address = "order_bill_address_attributes"
-    fill_in "#{address}_firstname", with: "Ryan"
-    fill_in "#{address}_lastname", with: "Bigg"
+
+    if ::Spree.solidus_gem_version <= Gem::Version.new('2.10.x')
+      fill_in "#{address}_firstname", with: "Ryan"
+      fill_in "#{address}_lastname", with: "Bigg"
+    else
+      fill_in "#{address}_name", with: "Ryan Bigg"
+    end
+
     fill_in "#{address}_address1", with: "143 Swan Street"
     fill_in "#{address}_city", with: "Richmond"
     select "Ohio", from: "#{address}_state_id"