Remove conflicting CSS rules on notifications, improve notifications table (#23565)

Remove conflicting CSS rules on notifications, improve notifications table (#23565)

Dropdowns on `/notifications/subscriptions` before and after:

<img width="157" alt="Screenshot 2023-03-18 at 20 37 12"
src="https://user-images.githubusercontent.com/115237/226133906-e4ad6a0a-de24-4324-8e1d-94081d23fe85.png">
<img width="152" alt="Screenshot 2023-03-18 at 20 41 29"
src="https://user-images.githubusercontent.com/115237/226134038-c3946c32-a424-4b92-ad15-890e1036cafe.png">

These selectors are meant to target the notification list which I
improved:

<img width="1145" alt="Screenshot 2023-03-19 at 01 52 11"
src="https://user-images.githubusercontent.com/115237/226147907-1c35736a-4bc9-4698-9813-21a20a1d2106.png">
<img width="1148" alt="Screenshot 2023-03-19 at 01 54 17"
src="https://user-images.githubusercontent.com/115237/226147920-626dbd84-11d3-48db-a177-6d808e3212c0.png">