fix(@schematics/angular): remove constructor from service template

Now that the style guide recommends to use `inject()`, having a constructor in a service is not really useful.

Author: cexbrayat

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

@@ -4,6 +4,5 @@ import { Injectable } from '@angular/core';
   providedIn: 'root'
 })
 export class <%= classify(name) %><%= classify(type) %> {
-
-  constructor() { }
+  
 }