funcref renamed to Callable

[jomiq]

Your Godot version:
v4.0.beta6.official [7f8ecffa5]

Issue description:
Documentation code examples mentions funcref which is superseded by Callable

URL to the documentation page:
Godot interfaces
Scene organizaton

[raulsntos]

This has been fixed by:

• rework two funcref code examples #6542
• Update some C# examples #7371
• C#: Replace FuncRef with Callable in outdated example #7505