Update expected diagnostics

Author: DougGregor

validation-test/compiler_crashers_2_fixed/0161-sr6569.swift

@@ -6,7 +6,7 @@ protocol P {
 
 struct Type<Param> {}
 extension Type: P where Param: P, Param.A == Type<Param> {
-  // expected-error@-1 6{{extension of generic struct 'Type' has self-referential generic requirements}}
+  // expected-error@-1 8{{extension of generic struct 'Type' has self-referential generic requirements}}
   // expected-note@-2 6{{through reference here}}
   // expected-error@-3 {{type 'Type<Param>' does not conform to protocol 'P'}}
   typealias A = Param