PHPUnit 9.6.15 Warning - The configuration file did not pass validation!

[otis22]

What steps will reproduce the problem?

With php v 8.0 or lower.

composer install
./vendor/bin/phpunit 

What is the expected result?

Test pass without warnings

What do you get instead?

Phpunit shows warning:

PHPUnit 9.6.15 by Sebastian Bergmann and contributors.

  Warning - The configuration file did not pass validation!
  The following problems have been detected:

  Line 27:
  - Element 'source': This element is not expected.

  Test results may not be as expected.

Additional info

| PHP version | 8.0

Element 'source' is valid element for PHPUnit ^10.
But in composer.json we have "phpunit/phpunit": "^9.6|^10.0"