[TASK] Streamline composer files

As the live environment is using PHP 7.4, the necessary adaptions are made:

composer update nimut/testing-framework --with-dependencies

=> 4.1.8 to 4.2.0 (adding PHP 7.4 compat in 4.2.0)

composer config sort-packages true

composer config platform.php 7.4.8

composer req "php:^7.4"