http: do not replace .read() in IncomingMessage

Remove the req._consumed property, as its use is completely
superseded and not needed anymore. This was being set in the
overridden .read().

PR-URL: https://github.com/nodejs/node/pull/18939


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>