Fix test which failed in isolation

It was transitively relying on the vertex model being loaded

activerecord/test/cases/relation/where_test.rb

@@ -7,6 +7,7 @@
 require 'models/edge'
 require 'models/topic'
 require 'models/binary'
+require 'models/vertex'
 
 module ActiveRecord
   class WhereTest < ActiveRecord::TestCase