doc: elevate diagnostic report to tier1

diagnostic report qualifies for all the criteria for
being in tier1. Classify it as such.

PR-URL: https://github.com/nodejs/node/pull/32732
Refs: https://github.com/nodejs/diagnostics/issues/369


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Matheus Marchini <mat@mmarchini.me>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>