Convert the font-size setting from px to pt by reverting commit
3e2c930ce0 ("ghostty: convert font-size setting from pt to px
(#1971)") because Ghostty measures font size in points, which was
previously incorrectly determined.
Link: https://github.com/nix-community/stylix/pull/1990
Reverts: 3e2c930ce0 ("ghostty: convert font-size setting from pt to px (#1971)")
Reviewed-by: pancho horrillo <pancho@pancho.name>