Lock PHPUnit-Bridge

Lock PHPUnit-Bridge

Version 4.4.0 & 5.0.0 will install PHPUnit 8.3.x by default which required PHP > 7.1.
We could lock the PHPUnit version using `SYMFONY_PHPUNIT_VERSION` env variable but we'll have an issue with PHP 5 then because there is no PHPUnit version compatible with both PHP 5 & PHP 7.

Also update deps:
  - Updating ocramius/package-versions (1.4.0 => 1.4.2)
  - Updating j0k3r/graby-site-config (1.0.94 => 1.0.95)
  - Updating php-http/client-common (2.0.0 => 2.1.0)
  - Updating symfony/mime (v4.3.8 => v4.4.0)
  - Updating white-october/pagerfanta-bundle (v1.2.4 => v1.3.1)
  - Installing phpseclib/phpseclib (2.0.23)
  - Updating php-amqplib/php-amqplib (v2.10.1 => v2.11.0)
  - Updating nette/php-generator (v3.2.3 => v3.3.1)
  - Updating zendframework/zend-diactoros (2.2.0 => 2.2.1)