doc: clarify ERR_INVALID_REPL_INPUT usage

The REPL documentation does not list prohibited inputs, but it does
explain the conditions under which ERR_INVALID_REPL_INPUT is used.
Update the error doc to indicate that.

PR-URL: https://github.com/nodejs/node/pull/37143


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>