Remove explicit dependency on System.Text.Json for modern .net

### Describe the bug
Now that all dependencies of MDS have removed their explicit reference to `System.Text.Json` for modern dotnet, please also remove it from MDS

### To reproduce
```xml

net8.0
true

```

Look into the generated `packages.lock.json` to see that the only reason `System.Text.Json` is included is because of the top level dependency of `Microsoft.Data.SqlClient`

### Expected behavior
No explicit dependency on `System.Text.Json`

### Further technical details
MDS 6.1, 7.0-preview
dotnet 8 and 9 (not dotnet10 somehow)