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

Update the current Json.NET dependency to System.Text.Json. Note that this
is required only for the following reasons:

- .NET Framework needs the package [1]
- We need a global dependency to work around [2] until the fix [3] is
released.

1: https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/overview#how-to-get-the-library
2: AzureAD/microsoft-authentication-library-for-dotnet#4108
3: AzureAD/microsoft-authentication-library-for-cpp#3522

Directory.Build.props

@@ -28,8 +28,8 @@
 
   <ItemGroup>
     <!-- Workaround https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/4108  -->
-    <PackageReference Include="Newtonsoft.Json">
-      <Version>13.0.1</Version>
+    <PackageReference Include="System.Text.Json">
+      <Version>7.0.2</Version>
     </PackageReference>
   </ItemGroup>