.NET 8 support

[VladislavAntonyuk]

error NU1107: WebApp -> Microsoft.Graph.Beta 5.55.0-preview -> Microsoft.Graph.Core 3.1.1 -> Microsoft.Kiota.Http.HttpClientLibrary 1.3.0 -> System.Text.Json (>= 6.0.0 && < 8.0.0)

[andrueastman]

Thanks for raising this @VladislavAntonyuk

We're tracking this via microsoft/kiota-serialization-json-dotnet#105. So we'll close this for now as a duplicate and resolve this soon.