Handbook: realign travel page headings

Why is this change being made?

The TOC for the Travel page of handbook did not make sense, with "tips on working remotely" being under Airbnb.

• Move Airbnb comment to within TripActions.
• Re-align "Tips on working remotely" and all sub-items to appropriate level.

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what