Update CloudMirrorPackage TargetPlatformVersion (#267)

Per the following issue update the TargetPlatformVersion to 10.0.22621.0 (from the pre-release version of 10.022598.0):
#267

Update Readme.md.

Author: smithmw

Samples/CloudMirror/CloudMirrorPackage/CloudMirrorPackage.wapproj

@@ -35,7 +35,7 @@
   <Import Project="$(WapProjPath)\Microsoft.DesktopBridge.props" />
   <PropertyGroup>
     <ProjectGuid>1fab5d02-237c-4b9c-b820-2eb7c3b6e63a</ProjectGuid>
-    <TargetPlatformVersion>10.0.22598.0</TargetPlatformVersion>
+    <TargetPlatformVersion>10.0.22621.0</TargetPlatformVersion>
     <TargetPlatformMinVersion>10.0.18362.0</TargetPlatformMinVersion>
     <DefaultLanguage>en-US</DefaultLanguage>
     <PackageCertificateKeyFile>CloudMirrorPackage_TemporaryKey.pfx</PackageCertificateKeyFile>

Samples/CloudMirror/README.md

@@ -31,7 +31,8 @@ The following functionality is implemented:
 
 **Note**   The Windows-classic-samples repo contains a variety of code samples that exercise the various programming models, platforms, features, and components available in Windows and/or Windows Server. This repo provides a Visual Studio solution (SLN) file for each sample, along with the source files, assets, resources, and metadata needed to compile and run the sample. For more info about the programming models, platforms, languages, and APIs demonstrated in these samples, check out the documentation on the [Windows Dev Center](https://dev.windows.com). This sample is provided as-is in order to indicate or demonstrate the functionality of the programming models and feature APIs for Windows and/or Windows Server.
 
-This sample was created for Windows 10 Version 1809 using Visual Studio and the Windows SDK 10.0.22598.0, but in many cases it will run unaltered using later versions. Please provide feedback on this sample!
+This sample was originally created for Windows 10 Version 1809 using Visual Studio and the Windows SDK 10.0.22598.0 (pre-release).  It has been updated to use Windows SDK 10.0.22621.0, but in many cases it will run unaltered using later versions. 
+Please provide feedback on this sample!
 
 To get a copy of Windows, go to [Downloads and tools](http://go.microsoft.com/fwlink/p/?linkid=301696).