Update warning about pseudo class first-child

[jeffvg]

Describe the bug

the warning about pseudo class first-child that would happen once in a few clicks to happening 14 times in one click. If you scroll to the bottom of "apps using blui" page then nav to roadmap page you should see this 14 times

What is the expected behavior?

no warnings

What are the steps to reproduce?

1. Go to...apps using blui page, scroll to bottom of page
2. Click on...roadmap page with dev tools open

Screenshots / Screen recording

Code snippet / Link to minimum reproduction example

updating all the first-child to first-of-type cleans up the warnings but unsure about final results

Your environment information

Suggested fix

Anything else to add?

emotion-js/emotion#2325

[huayunh]

This might have been fixed already in the latest PRs.

[huayunh]

• 7d9fe48
• f40e73c