Remove wrong dependency to service_id on parent_request_id

git-svn-id: http://svn.code.sf.net/p/itop/code/trunk@2636 a333f486-631f-4898-b8df-5754b55c2be0

datamodels/2.x/itop-request-mgmt-itil/datamodel.itop-request-mgmt-itil.xml

@@ -298,7 +298,6 @@
         <field id="parent_request_id" xsi:type="AttributeExternalKey">
           <filter><![CDATA[SELECT UserRequest WHERE id != :this->id AND status NOT IN ('rejected','resolved','closed')]]></filter>
           <dependencies>
-            <attribute id="service_id"/>
           </dependencies>
           <sql>parent_request_id</sql>
           <target_class>UserRequest</target_class>