Remove emotion first-child warnings in docs

[tmeasday]

Describe the bug

The pseudo class ":first-child" is potentially unsafe when doing server-side rendering. Try changing it to ":first-of-type".

[ndelangen]

I believe this has been fixed..?

[tmeasday]

I don't think so @ndelangen:

From https://635781f3500dd2c49e189caf-eldrpdmwma.chromatic.com/?path=/docs/storybook-blocks-examples-button--docs (latest build on next).

[tmeasday]

@ndelangen so what I think has happened here:

1. Originally there was an issue (in the manager) where our prior use of a special code comment to disable the warning wasn't working any more. This was due to a bug in Emotion.
2. The workaround for that was to use a special Emotion cache that just didn't send the warning, and removed the need for the special code comments, so we removed them.
3. Then later, in one PR, @Andarist did the same process as 2. for docs. However, he didn't merge it, as in the meantime:
4. He fixed the root problem in Emotion, and made a PR to update the version, and suggested reverting step 2.
5. However, that did't get merged because Emotion got updated separately.

OK, phew! But in all that, we never reverted step 2. And we never either added the cache or added the code comments to docs.

So I believe the right steps forward here are:

1. Revert step 2 (PR Turn off Emotion's warnings about potentially unsafe pseudo-selectors in SSR #18361)
2. Add special code comments (ignoreSsrWarning) to whichever docs components are triggering the warnings.

[Andarist]

Both the "what happened" and "what can be done" look OK to me. Let me know if I can assist you anyhow - if the problem won't go away I'm happy to take another look at this.

[tmeasday]

Thanks @Andarist - I'm hoping this should pretty mechanical now I know what's going on! :)

[shilman]

Whoopee!! I just released https://github.com/storybookjs/storybook/releases/tag/v7.1.0-alpha.0 containing PR #21213 that references this issue. Upgrade today to the @next NPM tag to try it out!

npx sb@next upgrade --prerelease

[shilman]

Gadzooks!! I just released https://github.com/storybookjs/storybook/releases/tag/v7.0.3 containing PR #21213 that references this issue. Upgrade today to the @latest NPM tag to try it out!

npx sb@latest upgrade