Update NuGet version

Author: nums11

Samples/MNIST/UWP/cs/MNIST_Demo.csproj

@@ -136,7 +136,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.AI.MachineLearning">
-      <Version>1.5.2</Version>
+      <Version>1.9.1</Version>
     </PackageReference>
     <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform">
       <Version>6.1.9</Version>