Enable FactoryBot/AttributeDefinedStatically

See https://robots.thoughtbot.com/deprecating-static-attributes-in-factory_bot-4-11

spec/factories/rooms.rb

@@ -4,13 +4,13 @@
 FactoryBot.define do
   factory :room do
     name { "Room #{Faker::Address.country}" }
-    size 4
+    size { 4 }
 
     venue
 
     factory :room_for_100 do
-      name 'Room for 100'
-      size 100
+      name { 'Room for 100' }
+      size { 100 }
     end
   end
 end