fix(infra): un-own forte-drop namespace from postgres app

Follow-up to 47d1f1e — the previous commit only updated postgres'
securityContext; this drops the explicit Namespace resource as the
Codex review flagged. Both apps still get the namespace created via
syncOptions: CreateNamespace=true.

infra/overlays/upc-dev/forte-drop-postgresql/forte-drop-postgresql.yaml

@@ -1,8 +1,3 @@
-apiVersion: v1
-kind: Namespace
-metadata:
-  name: forte-drop
----
 apiVersion: argoproj.io/v1alpha1
 kind: Application
 metadata: