Remove custom Results class

Update the SDK to use built-in Result factory class.

Author: martincostello

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "6.0.100-preview.7.21351.6",
+    "version": "6.0.100-preview.7.21354.4",
     "allowPrerelease": false,
     "rollForward": "latestMajor"
   }

src/TodoApp/Results.cs

@@ -8,7 +8,7 @@
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
     <PackageReference Include="JustEat.HttpClientInterception" Version="3.1.0" />
     <PackageReference Include="MartinCostello.Logging.XUnit" Version="0.1.1" />
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="6.0.0-preview.7.21329.3" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="6.0.0-preview.7.21330.3" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.10.0" />
     <PackageReference Include="Microsoft.Playwright" Version="1.12.2" />
     <PackageReference Include="Shouldly" Version="4.0.3" />