gitlab runner ci-runner-x86-03-shadow: higher artifact size limit

Trying to run some larger simulations now, and hitting the artifact size limit after completion: https://gitlab.torproject.org/jnewsome/sponsor-61-sims/-/jobs/28578#L9511

In that sim I'd increased the tor network size from 1% to 10%, but was still only simulating 10 minutes (vs the ~60m we'll probably want).

IIRC pastly previously recommended ~100 GB of storage for simulations; maybe try that?