Followup: update docs for new board list
See comment from @msedlakjakubowski on !149760 (comment 1902822738):
@clavimoniere Hey Chad, this MR is missing the UI text label and TW review. It should have included updates to https://docs.gitlab.com/ee/user/project/issue_board.html.
Would you mind following up with an MR to update steps and screenshots on that page? For sure in https://docs.gitlab.com/ee/user/project/issue_board.html#create-a-new-list and the
Assignee/Iteration/... lists
sections. Thanks!