style: fix linting issues met ESLint

backend/src/entities/assignments/group.entity.ts

@@ -4,12 +4,12 @@ import { Student } from '../users/student.entity.js';
 
 @Entity()
 export class Group {
-    @ManyToOne({ entity: () => Assignment, primary: true })
+    @ManyToOne({ entity: () => {return Assignment}, primary: true })
     assignment!: Assignment;
 
     @PrimaryKey({ type: 'integer' })
     groupNumber!: number;
 
-    @ManyToMany({ entity: () => Student })
+    @ManyToMany({ entity: () => {return Student} })
     members!: Student[];
 }