ci-runner-01 out of space

e.g. from https://gitlab.torproject.org/jnewsome/sponsor-61-sims/-/jobs/47427 :

$ apt-get install -y ca-certificates git
...
After this operation, 101 MB of additional disk space will be used.
E: You don't have enough free space in /builds/jnewsome/sponsor-61-sims/job-cache/apt/.
Cleaning up project directory and file based variables 00:01
ERROR: Job failed: exit code 1