Fix the spec generator to use test rather than unittest

pkg/analysis_server/tool/spec/codegen_matchers.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Code generation for the file "matchers.dart".
  */
 library codegen.matchers;
 
 import 'dart:convert';
@@ skipping 87 matching lines @@
 
   @override
   visitApi() {
     outputHeader();
     writeln();
     writeln('/**');
     writeln(' * Matchers for data types defined in the analysis server API');
     writeln(' */');
     writeln('library test.integration.protocol.matchers;');
     writeln();
-    writeln("import 'package:unittest/unittest.dart';");
+    writeln("import 'package:test/test.dart';");
     writeln();
     writeln("import 'integration_tests.dart';");
     writeln();
     writeln();
     for (ImpliedType impliedType in computeImpliedTypes(api).values) {
       makeMatcher(impliedType);
     }
   }
 
   @override
@@ skipping 64 matching lines @@
     for (TypeDecl choice in typeUnion.choices) {
       if (commaNeeded) {
         write(', ');
       }
       visitTypeDecl(choice);
       commaNeeded = true;
     }
     write('])');
   }
 }