Summary

Latest versions of all browsers now implement focusin & focusout natively
and they all converged on a common event order so it doesn't make much sense
for us to normalize it to a different order anymore.

Note that it means we no longer guarantee that focusin fires before focus
and focusout before blur.

-123 bytes

Fixes gh-4300

Checklist

• All authors have signed the CLA at https://cla.js.foundation/jquery/jquery
• New tests have been added to show the fix or feature works
• Grunt build and unit tests pass locally with these changes
• If needed, a docs issue/PR was created at https://github.com/jquery/api.jquery.com (I think we never documented event order guarantees)