RibbonGroup: Remove timeout

[cursork]

This is brittle and a bad experience: the intention is that the ribbon doesn't calculate heights and widths immediately, because it does not yet have all of the data it needs.

This was somewhat sufficient for creating a ribbon all in one go, but:

• It requires setting a timeout guaranteed to be greater than the time to receive all ribbon WC and WS instructions.
• Once eEX in Ribbons #335 and more are implemented, it will be trivial to break
• It already breaks if you're working one line at a time from Dyalog - no one is creating new objects quicker than the timeout

Other Ribbon issues than 335 might also be dependent on this work.