Remove unused typealias.

Author: rudkx

test/stdlib/Character.swift

@@ -306,7 +306,6 @@ CharacterTests.test(
   let asciiDomain = Array(0..<127)
   let ascii0to126 = asciiDomain.map({ UnicodeScalar(Int($0))! })
   let ascii1to127 = asciiDomain.map({ UnicodeScalar(Int($0 + 1))! })
-  typealias PredicateFn = (UnicodeScalar) -> (UnicodeScalar) -> Bool
   expectEqualMethodsForDomain(
     ascii0to126,
     ascii1to127,