benchmark: fix "comparisons"' typo

PR-URL: https://github.com/nodejs/node/pull/21085


Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Lance Ball <lball@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>