Only run did you mean spec it it's available

This spec has been problematic more than once, and I even removed it at
one point. I think this is a reasonable middle ground.

spec/acceptance/traits_spec.rb

@@ -313,7 +313,7 @@ describe "looking up traits that don't exist" do
       )
     end
 
-    it "maintains 'Did you mean?' suggestions at the end of the error message" do
+    it "maintains 'Did you mean?' suggestions at the end of the error message", skip: !defined?(DidYouMean) do
       define_class("User")
 
       FactoryBot.define do

spec/factory_bot/registry_spec.rb

@@ -28,7 +28,7 @@ describe FactoryBot::Registry do
       .to raise_error(KeyError, "Great thing not registered: \"object_name\"")
   end
 
-  it "includes a did_you_mean message" do
+  it "includes a did_you_mean message", skip: !defined?(DidYouMean) do
     registry = FactoryBot::Registry.new(:registry)
     registered_object = double(:registered_object)
     registry.register(:factory_bot, registered_object)