veyron/profiles: Fix build on Darwin

(Broken in https://veyron-review.googlesource.com/#/c/5008/)

Change-Id: I1435263b514e2cf0a33578fa5aa3528303547045
diff --git a/profiles/platform_darwin.go b/profiles/platform_darwin.go
index 933b589..e6b2af3 100644
--- a/profiles/platform_darwin.go
+++ b/profiles/platform_darwin.go
@@ -10,7 +10,6 @@
 	"fmt"
 
 	"veyron.io/veyron/veyron2"
-	"veyron.io/veyron/veyron2/security"
 )
 
 // Platform returns the description of the Platform this process is running on.
@@ -30,6 +29,5 @@
 		Machine: C.GoString(&t.machine[0]),
 		Node:    C.GoString(&t.nodename[0]),
 	}
-	d.Identity = security.FakePublicID(fmt.Sprintf("%s/%s/%s", d.Vendor, d.Model, d.Node))
 	return d, nil
 }