bug#59122: 29.0.50; global-text-scale-adjust not working

[Gregory Heytings]

> (set-face-attribute 'default nil :height (- (face-attribute 'default :height) 
> 6))
>
> the font size is decreased.  If I evaluate it more than once, the font 
> size decreases more with each additional invocation.

Thanks.  The safe fix should be to change 5 to 6 here.  Eli, do you agree, 
or is there something else to investigate?