Update rasta direct expectations.

pkg/front_end/test/fasta/rasta/issue_000007.dart.direct.expect

 library;
 import self as self;
 import "dart:core" as core;
 
 class Base extends core::Object {
-  constructor •() → self::Base
-    : super core::Object::•();
+  constructor •() → void
+    : super core::Object::•()
+    ;
 }
 class Mixin extends core::Object {
-  constructor •() → self::Mixin
-    : super core::Object::•();
+  constructor •() → void
+    : super core::Object::•()
+    ;
   method foo() → dynamic
     return core::print("foo");
 }
-class Sub extends self::Base+Mixin#0 {
-  constructor •() → self::Sub
-    : super self::Base+Mixin#0::•();
+class Sub extends self::Base&Mixin {
+  constructor •() → void
+    : super self::Base&Mixin::•()
+    ;
 }
-abstract class Base+Mixin#0 extends self::Base implements self::Mixin {
-  constructor •() → self::Base
-    : super self::Base::•();
+abstract class Base&Mixin extends self::Base implements self::Mixin {
+  constructor •() → void
+    : super self::Base::•()
+    ;
   method foo() → dynamic
     return core::print("foo");
 }
 static method main() → dynamic {
   new self::Sub::•().foo();
 }