build: turn off Codecov comments

Turns off coverage comments for the time being, until we can sort out
issues.

PR-URL: https://github.com/nodejs/node/pull/35800


Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>