tools: strip comments from lint-md rollup output

Refs: nodejs#41081 (comment)

PR-URL: nodejs#41092
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Tierney Cyren <hello@bnb.im>

Author: Trott