Mouse pointer shows wrong state when hovering over pop-out video overlay window

[kittykat]

Description

Mouse pointer icon doesn't correspond to actions which I can take on the pop-out video overlay (PIP)

Steps to reproduce

• Start a call and navigate to a different room so that the video overlay pops up
• Hover mouse pointer over overlay

Logs being sent: no

Version information

• Platform: web (in-browser)

For the web app:

• Browser: Chromium Version 92.0.4515.107 (Official Build)
• OS: Arch Linux (64-bit)
• URL: develop.element.io

Acceptance criteria for fix

• Mouse pointer icon correlates to overlay functionality (shows as clickable over buttons and areas which can be dragged, and as non-clickable over other areas)