Room List scrollbar is now harder to grab

### Steps to reproduce

Let Element update and try scrolling through the room list.

### Outcome

At least in Chromium, the scrollbar of the room list is now considerably harder to grab and use. The interactible area of the scrollbar has become smaller at the expense of the horizontal resize grab area.
The following two short videos demonstrate this. The first video is from before the update. You can still see me struggling, it wasn't ideal before, but it was usable. The second video is from after the update. In addition to the scrollbar being much harder to grab, the scrolling itself also feels considerably jankier.

https://github.com/user-attachments/assets/2bf9bde5-efe2-4655-8ca2-601b1821dc59

https://github.com/user-attachments/assets/2df0e256-6619-46cf-9180-dc6a8736724b

### Operating system

_No response_

### Browser information

Chromium Version 120.0.6099.199

### URL for webapp

_No response_

### Application version

_No response_

### Homeserver

_No response_

### Will you send logs?

Yes