Set memory_limit=-1 by default

[Ocramius]

Feature Request

Q	A
New Feature	yes
RFC	yes
BC Break	no

Summary

Our CI runs often run infection/infection, which is memory-intensive (unavoidable).

I think that setting a memory limit is an artificial limitation that is already well enforced by the GitHub Actions infrastructure (should we hit it): we should probably have memory_limit=-1 by default.

A memory limit enforced PHP-side doesn't give us any advantage, since it's mostly detrimental in non-web contexts anyway (and should be managed by a supervisor process anyway).

Ref: laminas/automatic-releases@af78115