Allow loading of C# files inside Script Editor, even if external DotNet editor is set

[yosimba2000]

This is in Godot 4.0.2

If a DotNet editor is set, and you try to load a C# script inside Script Editor, it won't load it inside Script Editor.
Instead, it will just open the file in your chosen DotNet editor.

This should be changed because if you write a Godot Tool Script in C#, you cannot easily load it into the Script Editor for execution.

The only workaround right now is to:

1. In Godot settings, set DotNet editor to none
2. You can now load C# script into Script Editor, and execute it.
3. Re-enable DotNet editor in Godot settings to allow editing in external editor.