The test is not nearly as unreliable as it used to be but we're still
seeing failures around the timing checks that will definitely be
affected by other tests running in other processes. So move it to
sequential.
Refs: https://github.com/nodejs/node/pull/35961#issuecomment-722222696
PR-URL: https://github.com/nodejs/node/pull/35996
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Rich Trott