doc: simplify process.binding() deprecation message

Keep the process.binding() deprecation message short and direct. In
addition to the usual benefits of doing that, it also means the message
is less likely to line-wrap once we move to a runtime deprecation.

PR-URL: https://github.com/nodejs/node/pull/25654


Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>