Adjust model 'answer-option' to backend implementation

src/app/models/answer-option.ts

 export class AnswerOption {
   label: string;
-  points: string;
+  points: number;
 
-  constructor(label: string, points: string) {
+  constructor(label: string, points: number) {
     this.label = label;
     this.points = points;
   }