[css-flexbox] editorial: typo in Flex Container cross-axis baseline set

[MatsPalmgren]

https://drafts.csswg.org/css-flexbox/#flex-baselines
In the definition of "first/last cross-axis baseline set", bullet 2 says:

Otherwise, the flex container has no first/last main-axis baseline set, ...

I think "main-axis" should be "cross-axis" there.

[fantasai]

Fixed, thanks!