Update c_sharp_differences.rst ToSignal example

[31]

This example should use SignalName to show the best practice, and in my opinion it should show the async method signature for context and as a hint for anyone new to await.

The SceneTreeTimer example does it this way: https://docs.godotengine.org/en/latest/classes/class_scenetreetimer.html

public async Task SomeFunction()
{
    GD.Print("Timer started.");
    await ToSignal(GetTree().CreateTimer(1.0f), SceneTreeTimer.SignalName.Timeout);
    GD.Print("Timer ended.");
}

Being able to pass a "raw" StringName is important for cross-language scripting when you don't have SignalName generation, but that detail belongs in the cross-language scripting page.

(From godotengine/godot-docs-user-notes#7 (comment))

[raulsntos]

LGTM. Thanks!

[skyace65]

Thanks!

[mhilbrunner]

Cherry-picked to 4.2.