chore: add warning encouraging react users to update mount function

[lmiller1990]

• Closes https://github.com/cypress-io/cypress/issues/23032

User facing changelog

N/A

Additional details

Add a useful warning for users on the old React API, cypress/react, who are using React 18. They can now take advantage of the React 18 integration, cypress/react18.

Steps to test

It's a trivial change. I tested it out, here's how it looks:

Before (warning in console and command log)

After (no, warning in console or command log)

How has the user experience changed?

PR Tasks

• [x] Have tests been added/updated?
• [ ] Has the original issue (or this PR, if no issue exists) been tagged with a release in ZenHub? (user-facing changes only)
• [ ] Has a PR for user-facing changes been opened in cypress-documentation?
• [ ] Have API changes been updated in the type definitions?

[cypress-bot[bot]]

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[cypress[bot]]

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Test summary

4379 • 0 • 51 • 0 • 0

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Run details

Project	cypress
Status	Passed
Commit	7002a6615c
Started	Aug 10, 2022 4:44 PM
Ended	Aug 10, 2022 4:55 PM
Duration	11:11 💡
OS	Linux Debian - 11.3
Browser	Firefox 99

View run in Cypress Dashboard ➡️

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[lmiller1990]

I will get this green and merge it up.