Update System.Text.Json in UnitTests.UWP project

Author: michael-hawker

UnitTests/UnitTests.UWP/UnitTests.UWP.csproj

@@ -124,7 +124,7 @@
       <!-- DO NOT UPGRADE THIS PACKAGE FROM 10.0.3, this is used for upgrade testing between 6.1.1 and 7.0.0 for the Object Serializers -->
     </PackageReference>
     <PackageReference Include="System.Text.Json">
-      <Version>4.7.2</Version>
+      <Version>5.0.2</Version>
     </PackageReference>
     <PackageReference Include="System.Xml.XPath.XmlDocument">
       <Version>4.3.0</Version>
@@ -548,4 +548,4 @@
   <Target Name="AfterBuild">
   </Target>
   -->
-</Project>
+</Project>