Remove invocation of drupal-phpunit-upgrade in Drupal 9

[gitressa]

Drupal 9 is using PHPUnit 8.5.15, and the problem in Can't run PHPUnit tests since Drupal 8.8.0 on PHP 7.3+ was:

ERROR: PHPUnit testing framework version 7 or greater is required when running on PHP 7.3 or greater. Run the command 'composer run-script drupal-phpunit-upgrade' in order to fix this.

Tests work without running composer run-script drupal-phpunit-upgrade in Drupal 9:

$ lando phpunit --group big_pipe
PHPUnit 8.5.15 by Sebastian Bergmann and contributors.

Testing 
...............................                                   31 / 31 (100%)
Time: 1.69 minutes, Memory: 881.00 MB
OK (31 tests, 253 assertions)

[serundeputy]

thanks @gitressa !

[gitressa]

Cool, thanks @serundeputy!