Fix flex-none in docs

[eAzizUrRehman]

On the https://tailwindcss.com/docs/flex page, I found issues in the Flex-None section.

1. In the preview, both the "div" having "flex-none" should have 100% opacity while the other "div" should be dim. Also, "div" having 03 should expand its width as it has "flex-1" property and not "div" having 02.
2. In the code, both the "flex-none" should be highlighted.

[reinink]

Hey thanks for pointing this out, I agree it's a little confusing right now. I've just made some changes to this page (#1804) that address these issues 👍

[eAzizUrRehman]

I'm glad you found the feedback helpful. Thanks 🖤