Notification count does not change when you change your notif options

[estellecomment]

Reproduce :
1 - join a channel. By default you have notifications for "All messages". The number of unread messages is displayed as a number next to the channel name.
2 - change notification option to "only mentions". Next to the channel name, the number disappears.

Observed : the total number of notifications, on the browser tab, stays the same. Its is confusing because you can't see where these unread messages could be, they don't correspond to the numbers on the individual channels.
Expected : the total number of notifications, on the browser tab, is reduced.

Refreshing the page fixes it. (so not too difficult to get rid of..)
Already present in 2.3.7.