Documentation-only: respond to Mark's comments on commit_checklist.md

This CL responds to Mark Goldstein's comments on commit_checklist.md.
Mark Goldstein was my instructor for the Technical Writing One course,
and as a follow-up exercise, he asked us to include him as a reviewer
on a documentation-related change. This doc will also form the basis
of my upcoming talk "Life of a CL" at Chrome University, so I want to
make sure it's in tip-top form!

Bug: None
Change-Id: I0aeefcbb149929969f15d375f55ea2d2d44684f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2045051
Reviewed-by: Aga Wronska <[email protected]>
Commit-Queue: Toby Huang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#743465}
1 file changed