doc: add a deprecation message for removing lttng

PR-URL: https://github.com/nodejs/node/pull/18982
Refs: https://github.com/nodejs/node/issues/18971
Refs: https://github.com/nodejs/node/pull/18975
Refs: https://github.com/nodejs/node/pull/18945


Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jackson Tian <shyvo1987@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>