TT#174405 actual_billing_profile fix billing_profile relation

* the relation was incorrectly performed by the contract_id
  instead of billing_profile_id

Change-Id: I34bd736ab8028d57d8ee69022b15711a6fc4bb1e

lib/NGCP/Schema/Result/actual_billing_profiles.pm

@@ -41,7 +41,7 @@ __PACKAGE__->belongs_to(
 __PACKAGE__->belongs_to(
   "billing_profile",
   "NGCP::Schema::Result::billing_profiles",
-  { id => "contract_id" },
+  { id => "billing_profile_id" },
   { cascade_copy => 0, cascade_delete => 0 },
 );