Clean up wording of client usage expectations

pkg/analysis_server/lib/plugin/edit/utilities/change_builder_dart.dart

Index: pkg/analysis_server/lib/plugin/edit/utilities/change_builder_dart.dart
diff --git a/pkg/analysis_server/lib/plugin/edit/utilities/change_builder_dart.dart b/pkg/analysis_server/lib/plugin/edit/utilities/change_builder_dart.dart
index e79204babc370f1fa8582e57eb746a9004339de4..7d0e0c7f6ca19ecd8d1264a2d5f22a9c1ade4d54 100644
--- a/pkg/analysis_server/lib/plugin/edit/utilities/change_builder_dart.dart
+++ b/pkg/analysis_server/lib/plugin/edit/utilities/change_builder_dart.dart
@@ -13,7 +13,7 @@ import 'package:analyzer/src/generated/engine.dart';
 /**
  * A [ChangeBuilder] used to build changes in Dart files.
  *
- * Clients are not expected to subtype this class.
+ * Clients may not extend, implement or mix-in this class.
  */
 abstract class DartChangeBuilder extends ChangeBuilder {
   /**
@@ -25,7 +25,7 @@ abstract class DartChangeBuilder extends ChangeBuilder {
 /**
  * An [EditBuilder] used to build edits in Dart files.
  *
- * Clients are not expected to subtype this class.
+ * Clients may not extend, implement or mix-in this class.
  */
 abstract class DartEditBuilder extends EditBuilder {
   /**
@@ -151,6 +151,6 @@ abstract class DartEditBuilder extends EditBuilder {
 /**
  * A [FileEditBuilder] used to build edits for Dart files.
  *
- * Clients are not expected to subtype this class.
+ * Clients may not extend, implement or mix-in this class.
  */
 abstract class DartFileEditBuilder extends FileEditBuilder {}