Bump minimal version of "phpunit-bridge"

[jderusse]

The PR #107 break other projects (like symfony: https://travis-ci.com/github/symfony/symfony/jobs/422680568)

The issue is: when installing dependencies with flag prefer-lowest, composer pick an old buggy version of phpunit-bridge (symfony's bug actually)

This PR bump the minimal version to 5.1 which has the same requirements than 4.4 (https://packagist.org/packages/symfony/phpunit-bridge#5.1.x-dev)

[jderusse]

Hmm... sadly, this does not work.... https://travis-ci.com/github/symfony/symfony/jobs/423288016

PHP Fatal error: Uncaught Error: Call to undefined method Symfony\Bridge\PhpUnit\DeprecationErrorHandler\Configuration::isGeneratingBaseline() in /home/travis/build/symfony/symfony/vendor/symfony/phpunit-bridge/DeprecationErrorHandler.php:213
Stack trace:
#0 [internal function]: Symfony\Bridge\PhpUnit\DeprecationErrorHandler->Symfony\Bridge\PhpUnit{closure}()
#1 {main}
thrown in /home/travis/build/symfony/symfony/vendor/symfony/phpunit-bridge/DeprecationErrorHandler.php on line 213
Fatal error: Cannot decl

When user use another instance of phpunit-bridge (think global install, or mono-repo), it conflicts with the one installed in vendors.

It could work only if both instances are exactly the same, or the project stop using it own instance of phpunit-bridge

Any idea how fix this.... @nicolas-grekas

[nicolas-grekas]

we should move this back to require-dev and add a note in the README that this should run with the bridge

[jderusse]

we should move this back to require-dev and add a note in the README that this should run with the bridge

What's about #112 ?