message: Update reviews.md - fix spelling issue
diff: @@ -8,7 +8,7 @@ When a PR is opened, you can request a reviewer by including `r?
  @username` in the PR description. If you don't do so, the highfive bot
  will automatically assign someone.
  -It is comment to leave a `r? @username` comment at some later point to
  +It is common to leave a `r? @username` comment at some later point to
  request review from someone else. This will also reassign the PR.
  ## bors
  @@ -40,6 +40,3 @@ done the review, and the code has not changed substantially since the
  review was done. Rebasing is fine, but changes in functionality
  typically require re-review (though it's a good idea to try and
  highlight what has changed, to help the reviewer).
  -
  -
  -
  