repl: remove unused variable from try catch

Catch statement defines err variable that is never used, so it
is safe to remove that.

PR-URL: https://github.com/nodejs/node/pull/23452


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>