Remove phpunit PHAR build from Git version control

[peter279k]

As title, the phpunit phar build is about the dependencies of required development.

I think we don't have to let this be in Git version control.

IMHO, the proper way is to remove this PHAR build and define correct phpunit version inside require-dev block on composer.json.

[liamdennehy]

@peter279k Did you mean to create this issue here? We were discussing this question in robrichards/xmlseclibs#200

Perhaps you meant to create this in https://github.com/robrichards/xmlseclibs/issues?

[peter279k]

Ok. Moving the issue to there.