`.app` files can't be deleted from the browse files window

### Tested versions

4.3.stable

### System information

Godot v4.3.stable - macOS 15.0.1 - Vulkan (Mobile) - integrated Apple M3 Max - Apple M3 Max (14 Threads)

### Issue description

Whether you consider this bug report an issue at all depends on your answer to this question: is a file with the `.app` extension a file or a folder?

One could argue: both. It's a package that Finder usually considers to be a single file, unless you right click on the `.app` file and choose Show Package Contents, after which you open the file as a folder.

This is perhaps a funny edge case, but I am of the opinion that the browser should be able to delete the `.app` file, hence why I'm issuing a bug report on it. I specifically right-mouse-clicked on it to delete it, so why shouldn't it work?

https://github.com/user-attachments/assets/bc65681d-95a3-43f9-af3e-22bc2757f441

### Steps to reproduce

Try to remove an `.app` file from the browse file window in Godot. It won't work.

### Minimal reproduction project (MRP)

n/a

Start by reproducing the deletion attempt in Godot's browse files window on macOS with a .app file, then trace the window's delete handling and how it distinguishes files from folders. Done means a .app package can be deleted through the context menu without breaking deletion of ordinary files or folders.

Written by the indexing model from the issue text.