Compatibility with PHP 8.0 and lower

[mvorisek]

#341 added phpunit 9.x support but it was releases after the compatibility with older PHP versions was dropped in #87 and #171.

In order to fully benefit from #341 and to allow this dependency in projects with PHP 8.1- support, the PHP version requirement must be lowered.

The latest johnkary/phpunit-speedtrap, at the time of writing this, requires PHP 7.2+ support - https://github.com/johnkary/phpunit-speedtrap/blob/master/composer.json#L22 so reintroducing support since this version would be welcomed to allow this package to be a real replacement.

Once the support for older PHP versions is added and at least one version tagged, the support for older PHP versions can be then removed again.

How to reproduce:

1. add ergebnis/phpunit-slow-test-detector dependency to a PHP 7.4 - 8.3 project
2. run composer update on/using PHP 7.4 platform

[localheinz]

Fixed with #375 and #390.

[localheinz]

@mvorisek

Released as ergebnis/phpunit-slow-test-detector:2.5.0.