Standardise on avoiding except lists for check_api_readable

Although this is technically duplicative, it's much easier to read
and therefore to maintain, particularly if you put the _readable one
first.

app/controllers/api/ways_controller.rb

@@ -1,7 +1,7 @@
 module Api
   class WaysController < ApiController
+    before_action :check_api_readable
     before_action :check_api_writable, :only => [:create, :update, :delete]
-    before_action :check_api_readable, :except => [:create, :update, :delete]
     before_action :authorize, :only => [:create, :update, :delete]
 
     authorize_resource