chore: bump dev dependencies

[Chris53897]

use ProphecyTrait

I need to check if ci-pipeline is green.

[dbu]

okay, we found a good reason to drop the php 7 versions. (that will also allow to reduce the range of allowed require-dev dependencies, we no longer will need 3 major versions of phpunit and prophecy...)

do you want to drop the 7 versions in a seprate MR (and add a changelog entry about it)? and then pick up this again?

[Chris53897]

Yes i will drop php 7 in a seperate PR