Increase toolbox memory limit

What does this MR do and why?

Related to #388305 (closed) and https://gitlab.com/gitlab-org/quality/engineering-productivity-infrastructure/-/issues/73

Error 137 seems to be an Out Of Memory (OOM) error.

The chosen fix is to increase the memory limit of the container that's being killed (in this instance, the toolbox container).

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.