Working on Tickets page: De-duplicate/Tighten-up "setting expectations" sections

There are currently two sections on setting expectations:

• Working with customers > Setting expectations
• Working on individual tickets > Ticket statuses > Using the On-Hold ticket status > Set clear expectations

The current state of these sections are fragmented and largely duplicate each other. We should consolidate them into a single section and insert a reference to that section wherever appropriate.

From @cynthia gitlab-com/www-gitlab-com!95157 (comment 761836801):

I think something went missing here?

I believe this line (and the ones following it) were meant for times when the ticket is set to "Open" or "On-Hold" when we say we need more time to investigate, or we're waiting for someone else

From @cynthia gitlab-com/www-gitlab-com!95157 (comment 761836819)

This seems to be mostly a repeat of the "Settings expectations" section?