Fix test for precedence groups.

Author: rjmccall

validation-test/stdlib/MicroStdlib/Inputs/Swift.swift

@@ -2,6 +2,8 @@
 // A bare-bones Swift standard library
 //
 
+precedencegroup AssignmentPrecedence { assignment: true }
+
 public enum Optional<Wrapped> {
   case none
   case some(Wrapped)

validation-test/stdlib/MicroStdlib/MicroStdlib.swift

@@ -9,5 +9,4 @@
 // RUN: %target-run %t/hello | FileCheck %s
 // REQUIRES: executable_test
 // CHECK: Hello
-// REQUIRES: rdar27558848