.Net: Updated package version to 1.21.1 (#8992)

Author: dmytrostruk

dotnet/nuget/nuget-package.props

@@ -1,7 +1,7 @@
 <Project>
   <PropertyGroup>
     <!-- Central version prefix - applies to all nuget packages. -->
-    <VersionPrefix>1.21.0</VersionPrefix>
+    <VersionPrefix>1.21.1</VersionPrefix>
     <PackageVersion Condition="'$(VersionSuffix)' != ''">$(VersionPrefix)-$(VersionSuffix)</PackageVersion>
     <PackageVersion Condition="'$(VersionSuffix)' == ''">$(VersionPrefix)</PackageVersion>