solve_ndisj: try harder

In my logically atomic stack, the following goal fails to be solved currently but is solved after this patch:

⊤ ∖ ↑stackN ⊆ ⊤ ∖ ↑offerN ∖ ↑protoN

where

Definition stackN : namespace := nroot .@ "logatom_stack".
Definition offerN : namespace := nroot .@ "logatom_stack" .@ "offer".
Definition protoN : namespace := nroot .@ "logatom_stack" .@ "protocol".

theories/namespaces.v

@@ -101,5 +101,5 @@ Ltac solve_ndisj :=
   repeat match goal with
   | H : _ ∪ _ ⊆ _ |- _ => apply union_subseteq in H as [??]
   end;
-  solve [eauto with ndisj].
+  solve [eauto 10 with ndisj].
 Hint Extern 1000 => solve_ndisj : solve_ndisj.