patch 9.2.0468: popups: not correctly updated from a CmdlineChanged autocommand

patch 9.2.0468: popups: not correctly updated from a CmdlineChanged autocommand

Problem:  popup_show() from a CmdlineChanged autocommand doesn't update
          the screen (Mao-Yining)
Solution: Refresh the screen when popups need redraw
          (Yasuhiro Matsumoto).

popup_settext()/popup_show() called from a CmdlineChanged autocommand
did not refresh the screen because cmdline mode normally skips
update_screen(), so async info-popup updates only became visible after
a manual :redraw.  Refresh the screen when popups need redrawing right
after the autocommand.

fixes:  #20175
closes: #20179

Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>