Allow symfony/http-foundation ^6.0 instead of 6.0 to support symfony 6.x

[robertfausk]

It should be symfony/http-foundation ^6.0 instead of 6.0, am I correct?

Otherwise I am currently not able to use it with a symfony 6 project when restricting to symfony 6.1.* in composer.json.
See image below:

When I restrict symfony to 6.0.* in composer.json then I can use soyuka contexts.

[robertfausk]

Just saw that there is already a PR in #5

I am keen on getting this merged :-)

@soyuka Feel free to close my PR in favor of #5