Fix test that didn't actually improve

Author: DougGregor

test/Constraints/keypath.swift

@@ -41,9 +41,10 @@ func testFunc() {
   let _: (S) -> Int = \.i
   _ = ([S]()).map(\.i)
 
+  // FIXME: A terrible error, but the same as the pre-existing key path
+  // error in the similar situation: 'let _ = \S.init'.
   _ = ([S]()).map(\.init)
-  // expected-error@-1 {{key path cannot refer to static member 'init()'}}
-  // expected-error@-2 {{key path value type '() -> S' cannot be converted to contextual type '_'}}
+  // expected-error@-1 {{type of expression is ambiguous without more context}}
 
   let kp = \S.i
   let _: KeyPath<S, Int> = kp // works, because type defaults to KeyPath nominal