Update uptime alert notification docs

[InterstellarStella]

Which part? Which one?

Uptime monitoring

Description

In this part of the uptime monitoring docs, for the notification setup, the text and screenshot indicate that the user should choose the "Uptime" option. However, this has recently been changed, and the user needs to select "Outage" now. This is correctly indicated in our knowledge base here.

Suggested Solution

Update the text and screenshot to show "Outage" instead of "Uptime".

[gaprl]

Fixed by #14444