history: drop second string arg to attach-history

history: drop second string arg to attach-history

All callers pass popup:close as second arg to attach-history.
This is a command that history catches so as to save the new
entry into this history.
Handling it requires complexity that I would rather avoid.
So for now - just assume it is always popup:close.
If a need appears, I can come up with some other way to
achieve the same effect.

Signed-off-by: NeilBrown <neil@brown.name>