[Test] Update error message in validation test.

Author: hborla

validation-test/compiler_crashers_2_fixed/0159-rdar40009245.swift

@@ -4,5 +4,5 @@ protocol P {
     associatedtype A : P where A.X == Self
     // expected-error@-1{{'X' is not a member type of type 'Self.A'}}
     associatedtype X : P where P.A == Self
-    // expected-error@-1{{associated type 'A' can only be used with a concrete type or generic parameter base}}
+    // expected-error@-1{{cannot access associated type 'A' from 'P'; use a concrete type or generic parameter base instead}}
 }