bug#44315: display property :align-to doesn't update with text-scale-mode

[Stefan Kangas]

The display property :align-to space doesn't update when I change the
text-scale using `text-scale-increase', `text-scale-decrease' or
`text-scale-adjust', as can be seen here:

0. emacs -Q
1. Evaluate:
(progn (insert (make-string 60 ?*) "\n")
       (insert (propertize " " 'display '(space :align-to 60)))
       (insert "*\n")
       (text-scale-increase 1))

The result is that the first line extends beyond the position of the
"*" character on the second line.

I expect them to line up.