Some menus unexpectedly move to the left

### What Happened?

This is an odd one. Some menus in Firefox are suddenly displaced to the left while interacting with them.

https://github.com/user-attachments/assets/7e419b12-8313-4437-ba08-e655df86835a

### Steps to Reproduce

This happens in two places:
1. When opening the tab list menu on the upper right corner.
2. When opening bookmark folders on the bookmarks toolbar.

Easiest way to reproduce:
1. Open the tab list menu.
2. Move your cursor around until you notice that the menu items are being highlighted while hovering an area to the left of the menu.
3. To make the menu move left, move your cursor on top of a menu item and hold it there for a moment (to show a tooltip).

### Expected Behavior

The menu should not move that way. I use the GNOME desktop too, and it doesn't happen there.

### OS Version

8.x (Circe)

### OS Architecture

amd64 (on most hardwares)

### Session Type

Secure Session (Wayland, This is the default)

### Software Version

Latest release (I have run all updates)

- Firefox 146.0 (Snap)
- Gala 8.4.0

### Log Output

```shell

```

### Hardware Info

- GPU: AMD® Radeon RX 6600
- Monitor resolution: 2560x1080
- Mouse and keyboard.