Unless I missed it, you can't remove panels from dashboards right now.
I recently added "headless" flag, but I think we should back that out and do this instead:
- there's a "frame mode" or "header mode" or something, which has three values: "none", "normal", and "arrange" (or whatever)
- `none`: No header, for panels in panels.
- `normal`: Normal header, for most panels on Dashboards. Might get sleeker or something after T5005.
- `arrange`: header with remove action (and maybe edit)
Then make the arrange view render panels in "arrange" mode, give 'em a delete button, and make that kick them off the board.