These tests spawn many workers, which may be CPU intensive causing
timeouts (see the referenced PR for more details). Let's move them
to sequential.
Refs: https://github.com/nodejs/node/pull/44090
PR-URL: https://github.com/nodejs/node/pull/44139
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
