`get_overlapping_areas()` detects areas with `monitorable == false`

### Tested versions

Reproducible in: 3.5.3.stable

### System information

Windows 11 - Godot v3.5.3.stable

### Issue description

When polling for any overlapping areas within a specific layer using `get_overlapping_areas()`, areas are found to be overlapping even when their `monitorable` values are false.
This happened consistently in my game project, where I worked around it by removing and re-adding the target node from their collision layer, which worked out ok, but upon creating an MRP I got the error inconsistently.

Here's a video of it happening on some runs but not others:

https://github.com/godotengine/godot/assets/3142110/fd9297e7-6558-4a95-a76a-49027106d717

### Steps to reproduce

have an area 2d node `target` with a collision layer = n and `monitorable` value equal to `true`
have an area 2d node `monitor` with a collision mask = n and `monitoring` value equal to `true`
put both nodes within a scene and make sure their areas overlap.
on the scene's `_process(_delta)` method, call `monitor.get_overlapping_areas()` and observe `target` area is found to be overlapping. call `$Target.set_deferred("monitorable", false)`, and notice it sometimes is found to be overlapping even when it's `monitorable` value equals `false`.

### Minimal reproduction project (MRP)

[bug_report_MRP.zip](https://github.com/user-attachments/files/15949581/bug_report_MRP.zip)

Start by running the attached minimal reproduction project on Godot 3.5.3 and tracing Area2D's get_overlapping_areas() behavior after Target.set_deferred("monitorable", false). Inspect the implementation entry points for get_overlapping_areas and monitorable handling. Done means the target is not reported after monitorable becomes false, consistently across reproductions.

Written by the indexing model from the issue text.