docs(plan)!: remove the order field and the numbered column master
A total order over twenty epics was a lie that cost something to maintain. Inserting one at the front renumbered every file beneath it and every row in the register, so two branches each adding an epic conflicted by construction, over a number neither of them cared about — which is exactly what happened between this branch and the camo/invite stack. The Open table still reads roughly top to bottom and that is now the whole of the ordering. What actually constrains the work is dependsOn and status, both of which are per epic and true independently of what anybody else is doing. Moving an epic is moving one line. Breaking for anything already reading the frontmatter: `order` is gone, not optional. Change-Id: Ica1bf689a9d7f10dd930fdc8034f09346d2f0407