doc: improve triaging text in issues.md

Remove a double negative and many superfluous sentences. The sentiment
in the removed material is good, but we already tell people that
discussion should be focused, helpful, and professional. Having two
extra paragraphs greatly reduces the likelihood that people will read
the material.

PR-URL: https://github.com/nodejs/node/pull/34164


Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>