Fix a small example so that the example matches the narrative within. (#2613)

Specifically, the narrative is talking about sending the variable 't' not the
variable 'ns'.

Author: gottesmm

proposals/0430-transferring-parameters-and-results.md

@@ -213,15 +213,15 @@ func h() async {
   // This is a `sending` value.
   let ns = Nonsending()
 
-  // This also a `sending value.
+  // This also a `sending` value.
   let ns2 = NonSendable()
 
   // Since both ns and ns2 are disconnected, the region associated with
   // tuple is also disconnected and thus 't' is a `sending` value...
   let t = (ns, ns2)
 
   // ... that can be sent across a concurrency boundary safely.
-  await sendToMain(ns)
+  await sendToMain(t)
 }
 ```