OOM in 6.3.10

[taymonbeal]

https://github.com/google/fledge-shim/runs/4765450371

Upgrading Karma from 6.3.9 to 6.3.10 causes what appear to be out-of-memory errors on GitHub Actions. Rerunning the job doesn't help. The PR is from Dependabot and makes no other changes, and everything's passing at head, so I figure this has to somehow be a Karma regression.

[devoto13]

See #3738.