Onboarding: add wording to provide more opportunities/flexibility on pairing early

This came up during the latest skip level with @lbot

From the doc:

1. Jio: brought up recently with manager. Alongside with existing onboarding, what can be worked on at the same time to get a better core understanding of GitLab.
   1. Arty: could pods help? Thinking of the “GitLab features” pod which covers “core” features; and instance management one.
   2. Kaitlyn: what if we focused on getting help, how to rely on others?
   3. Lee: maybe we start with first pairing session, then keep going
2. Julie: other companies, that’s not how it worked. Still difficult to throw something on people’s calendar.
3. Greg Myers: I'd encourage folks to CC themselves and follow along on tickets assigned to tenured GitLab team members until they're comfortable sending ticket replies themselves. Is CCing yourself to interesting tickets currently mentioned anywhere in our onboarding?
4. Greg Myers: "pairing" early on can be awkward if one person is picking all the tickets and sending all the replies. What about Support shadow program?
   1. Kaitlyn Chappell +1 this is how a lot of orgs I’ve worked at did onboarding. Shadow where the more tenured person leads, then swap to the new person leading and the tenured person helping.
5. Lee: a quick thing we can do is reach out to new hires for pairing.

Proposal

whatever makes sense, possibly:

it makes sense to "reorder" the modules a little but also emphasize the pairing "module" should be done parallel to onboarding