src: remove dead code in InternalMakeCallback

Remove unneeded condition as the first line in function already
ensures that recv can't be empty.

PR-URL: https://github.com/nodejs/node/pull/31622


Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yihong Wang <yh.wang@ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>