dependencies: update json.net to system.text.json

Update global reference to Json.NET (Newtonsoft.Json) to System.Text.Json.
Note that this is only required for .NET Framework and can be removed when
GCM migrates off it.

Author: ldennington

Directory.Build.props

@@ -26,10 +26,9 @@
     <GenerateWindowsAppManifest Condition="'$(GenerateWindowsAppManifest)' == '' AND '$(OSPlatform)' == 'windows' AND '$(_IsExeProject)' == 'true'">true</GenerateWindowsAppManifest>
   </PropertyGroup>
 
-  <ItemGroup>
-    <!-- Workaround https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/4108  -->
-    <PackageReference Include="Newtonsoft.Json">
-      <Version>13.0.1</Version>
+  <ItemGroup Condition = "'$(TargetFramework)' == 'net472'">
+    <PackageReference Include="System.Text.Json">
+      <Version>7.0.2</Version>
     </PackageReference>
   </ItemGroup>