refactor(@schematics/angular): remove empty constructor from directive template

Align directive template with the component template cleanup done in 301b566.

Author: cexbrayat

packages/schematics/angular/directive/files/__name@dasherize__.__type@dasherize__.ts.template

@@ -5,7 +5,4 @@ import { Directive } from '@angular/core';
   standalone: false,<%}%>
 })
 export class <%= classifiedName %> {
-
-  constructor() { }
-
 }