bump phpunit-bridge version constraint

[jrushlow]

v5.4.17 of phpunit-bridge fixed compatibility with doctrine/annotations:^2.0.
https://github.com/symfony/symfony/pull/48718/files#diff-7b61897762550adef47d038e61dbb44e9759b80179c8c7674fc2300c207fe751

Without the version bump to at least 5.4.17 - CI fails against 5.4.* w/ --prefer-lowest dependencies. phpunit-bridge:^5.4.7 is the lowest, but not compatible w/ MakerBundle as doctrine/annotations isn't needed.

Fixes:

PHP Fatal error:  Uncaught Error: Call to undefined method Doctrine\Common\Annotations\AnnotationRegistry::registerLoader() 
in /home/runner/work/maker-bundle/maker-bundle/vendor/symfony/phpunit-bridge/bootstrap.php:34

in several tests.

[weaverryan]

Thanks Jesse!