fix: rollback isValid() in retrieveSchema() to validateFormData()

[cewald]

Reasons for making this change

fixes #4357

This reverts commit ff46301

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests. I've run npx nx run-many --target=build --exclude=@rjsf/docs && npm run test:update to update snapshots, if needed.
  • I've updated docs if needed
  • I've updated the changelog with a description of the PR
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[heath-freenome]

Looks good. One question and a small change to the CHANGELOG.md and you are good to go

[heath-freenome]

@cewald It looks like something in the utils tests are breaking. Can you please take a look... Also there are a few questions/concerns to address

[cewald]

I did not had time for checking the tests yet – but I actually "just reverted the changes". So there might be changes in the meantime that rely on the new version of code. Idk. I dont think I find time to debug those tests anytime soon, as I am not that much into the code and would need some time for research.

[heath-freenome]

Closing in favor of #4723