util: rename util.inspect argument

util.inspect can actually receive any property and the description
was wrong so far. This fixes it by renaming the argument to
value and also updating the description.

Backport-PR-URL: https://github.com/nodejs/node/pull/19230
PR-URL: https://github.com/nodejs/node/pull/17576


Reviewed-By: Anna Henningsen <anna@addaleax.net>