fixing InstallResult type definition

Author: chrmod

index.bs

@@ -11324,9 +11324,9 @@ ExtensionsCommand = (
 [=local end definition=]
 
 <pre class="cddl local-cddl">
-ExtensionsResult = (
+ExtensionsResult = {
   extensions.InstallResult
-)
+}
 </pre>
 
 ### Types ### {#module-extensions-types}