Make the UpdateRecevier not wait for each handler

[XSilverTH]

I have no idea if awaiting each handler was intended behavior but it seems wrong to me to freeze the whole bot just because a command is taking long to execute

[Rikitav]

The receiver is not a component that is responsible for the execution of handlers. This is handled by IUpdateRouter, the standard implementation uses a pool to manage the life of handlers. For more info check : https://github.com/Rikitav/Telegrator/blob/master/Telegrator/Polling/UpdateRouter.cs

[XSilverTH]

i still don't know if executing handlers synchronously was intended behaviour or not
considering MaximumParallelWorkingHandlers exists i assume not