[css-fonts-4][varfont] Over specification of axis wording.

[bungeman]

https://drafts.csswg.org/css-fonts-4/#propdef-font-variation-settings

Replace

If the same axis name appears twice, the second one supercedes the first.

with

If the same axis name appears more than once, the value associated with the last appearance supersedes any previous value for that axis.

or something at least as clear (and doesn't mis-spell 'supercedes').

[litherum]

Sounds good to me.

In the future, for small stuff like this, feel free to submit a pull request.