Update ASP.NET Core 3.1-to-5.0 migration doc for Preview 2 release (#17591)

Author: scottaddie

aspnetcore/includes/net-core-prereqs-mac-5.0.md

@@ -1,4 +1,2 @@
-Support expected in version 8.6
-
-<!-- * [Visual Studio for Mac version 8.6 or later](https://visualstudio.microsoft.com/vs/mac/)
-* [!INCLUDE [.NET 5.0 SDK](~/includes/5.0-SDK.md)] -->
+* [Visual Studio for Mac version 8.6 or later](/visualstudio/releasenotes/vs2019-mac-preview-relnotes)
+* [!INCLUDE [.NET 5.0 SDK](~/includes/5.0-SDK.md)]

aspnetcore/migration/31-to-50.md

@@ -4,7 +4,7 @@ author: scottaddie
 description: Learn how to migrate an ASP.NET Core 3.1 project to ASP.NET Core 5.0.
 ms.author: scaddie
 ms.custom: mvc
-ms.date: 03/24/2020
+ms.date: 04/02/2020
 uid: migration/31-to-50
 ---
 # Migrate from ASP.NET Core 3.1 to 5.0
@@ -40,7 +40,7 @@ If you rely upon a [global.json](/dotnet/core/tools/global-json) file to target
 {
   "sdk": {
 -    "version": "3.1.200"
-+    "version": "5.0.100-preview.1.20155.7"
++    "version": "5.0.100-preview.2.20176.6"
   }
 }
 ```
@@ -68,8 +68,8 @@ In the project file, update each `Microsoft.AspNetCore.*` and `Microsoft.Extensi
 <ItemGroup>
 -    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="3.1.2" />
 -    <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="3.1.2" />
-+    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="5.0.0-preview.1.20124.5" />
-+    <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="5.0.0-preview.1.20120.4" />
++    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="5.0.0-preview.2.20167.3" />
++    <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="5.0.0-preview.2.20160.3" />
 </ItemGroup>
 ```