Working on Tickets page: Expand on "Breach clocks" section

The "Breach clocks" section should be expanded to include guidance around the difference between FRTs (SLAs / contractual obligations) and NRTs (SLOs / not contractual obligations), and the differing priorities we accord to them.

Also, the current content is a near duplicate of the "make sure to reply to the user" section under "Ticket statuses" as per @cynthia's observations in gitlab-com/www-gitlab-com!95157 (comment 761836825):

a near duplicate of the "make sure to reply to the user"?

As per my previous comment, this might be better as a briefer note in the status section