Generate constants in server as we do in plugin

pkg/analysis_server/lib/protocol/protocol_generated.dart

Index: pkg/analysis_server/lib/protocol/protocol_generated.dart
diff --git a/pkg/analysis_server/lib/protocol/protocol_generated.dart b/pkg/analysis_server/lib/protocol/protocol_generated.dart
index 52637211fc82caf6a34403cca4354483acfc3ee0..8f14c4164ba1238ccf8bf07081eb7e79a48bda50 100644
--- a/pkg/analysis_server/lib/protocol/protocol_generated.dart
+++ b/pkg/analysis_server/lib/protocol/protocol_generated.dart
@@ -7597,12 +7597,12 @@ class EditListPostfixCompletionTemplatesResult implements ResponseResult {
   List<PostfixTemplateDescriptor> _templates;
 
   /**
-   * The list of available template.
+   * The list of available templates.
    */
   List<PostfixTemplateDescriptor> get templates => _templates;
 
   /**
-   * The list of available template.
+   * The list of available templates.
    */
   void set templates(List<PostfixTemplateDescriptor> value) {
     assert(value != null);