Remove unused usings from example and exemplar

Author: ErikSchierboom

exercises/concept/attack-of-the-trolls/.meta/Exemplar.cs

@@ -1,5 +1,3 @@
-using System;
-
 enum AccountType
 {
     Guest,

exercises/concept/authentication-system/.meta/Exemplar.cs

@@ -1,4 +1,3 @@
-using System.Collections.Generic;
 using System.Collections.ObjectModel;
 
 public class Authenticator

exercises/concept/beauty-salon-goes-global/.meta/Exemplar.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Globalization;
 using System.Runtime.InteropServices;
 

exercises/concept/bird-watcher/.meta/Exemplar.cs

@@ -1,5 +1,3 @@
-using System;
-
 class BirdCount
 {
     private int[] birdsPerDay;

exercises/concept/booking-up-for-beauty/.meta/Exemplar.cs

@@ -1,5 +1,3 @@
-using System;
-
 static class Appointment
 {
     public static DateTime Schedule(string appointmentDateDescription)

exercises/concept/building-telemetry/.meta/Exemplar.cs

@@ -1,6 +1,3 @@
-using System;
-
-
 public class RemoteControlCar
 {
     private int batteryPercentage = 100;

exercises/concept/calculator-conundrum/.meta/Exemplar.cs

@@ -1,5 +1,3 @@
-using System;
-
 public static class SimpleCalculator
 {
     public static string Calculate(int operand1, int operand2, string operation)

exercises/concept/developer-privileges/.meta/Exemplar.cs

@@ -1,6 +1,3 @@
-using System;
-using System.Collections.Generic;
-
 public class Authenticator
 {
     public Identity Admin { get; } = new Identity

exercises/concept/faceid-2/.meta/Exemplar.cs

@@ -1,6 +1,3 @@
-using System;
-using System.Collections.Generic;
-
 public class FacialFeatures
 {
     public string EyeColor { get; }

exercises/concept/football-match-reports/.meta/Exemplar.cs

@@ -1,5 +1,3 @@
-using System;
-
 public static class PlayAnalyzer
 {
     public static string AnalyzeOnField(int shirtNum)