test: skip some pummel tests on slower machines

Skipped the longest-running pummel tests on the Raspberry Pi devices in
CI.

Refs: https://github.com/nodejs/node/pull/34289#issuecomment-823354459

PR-URL: https://github.com/nodejs/node/pull/38394


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Filip Skokan <panva.ip@gmail.com>