doc: use imperative in COLLABORATOR_GUIDE

Instead of wording the paragraph about communicating deprecations with
the ecosystem as if it were directed at the ecosystem, write it as in
imperative directed at the collaborator, since that is the audience for
the COLLABORATOR_GUIDE. Instead of assuring the reader that a best
effort will be made, instruct the reader to make the effort to
communicate with the ecosystem.

PR-URL: https://github.com/nodejs/node/pull/21340


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>