remove some redundant usings

Author: SimonCropp

samples/EarlyInitializationSample/Startup.cs

@@ -1,8 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;

samples/InlineInitializationSample/Startup.cs

@@ -1,8 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;