doc: remove personal pronoun usage in policy.md

Per our style guide, avoid personal pronouns (I, you, we, etc.) in
reference documentation.

PR-URL: https://github.com/nodejs/node/pull/32142


Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>