Remove invalid field mapping

Author: yceruto

tests/fixtures/MakeEntityXmlMappingError/config/doctrine/User.orm.xml

@@ -7,6 +7,5 @@
         <id name="id" type="integer">
             <generator strategy="AUTO" />
         </id>
-        <one-to-many field="avatars" target-entity="UserAvatar" mapped-by="user" />
     </entity>
-</doctrine-mapping>
+</doctrine-mapping>