Revert "[region-isolation] Add a test showing that we do not infer nonisolated(unsafe) onto named closures."

This reverts commit 4ccb39e.

Author: gottesmm

test/Concurrency/transfernonsendable_nonisolatedunsafe.swift

@@ -1028,18 +1028,4 @@ func closureTests() async {
     // expected-note @-1 {{Passing value of non-Sendable type '() async -> ()' as a 'sending' argument to static method 'detached(priority:operation:)' risks causing races in between local and caller code}}
     Task.detached { _ = x4a; _ = x4b } // expected-note {{access can happen concurrently}}
   }
-
-  // The reason why this works is that we do not infer nonisolated(unsafe)
-  // passed the begin_borrow [var_decl] of y. So we think the closure is
-  // nonisolated(unsafe), but its uses via the begin_borrow [var_decl] is
-  // not.
-  func testNamedClosure() async {
-    nonisolated(unsafe) let x = NonSendableKlass()
-    let y = {
-      _ = x
-    }
-    sendingClosure(y) // expected-warning {{sending 'y' risks causing data races}}
-    // expected-note @-1 {{'y' used after being passed as a 'sending' parameter}}
-    sendingClosure(y) // expected-note {{access can happen concurrently}}
-  }
 }