[FEATURE] Clarify wording of maintainer nomination requirements

Is your feature request related to a problem?

Reading https://github.com/opensearch-project/.github/blob/main/RESPONSIBILITIES.md#becoming-a-maintainer, it's not explicit say whether the nominating maintainer can vote or count as part of the 3 upvotes.

I consulted Claude "for becoming a maintainer, does the nominating maintainer count as an upvote?", it also could not be sure from the wording:

The doc doesn't explicitly say, but the wording implies yes — the nominating maintainer's vote counts.

The Nomination section says the nominating maintainer "starts a private e-mail thread... to discuss nomination" and "at least three positive (+1) maintainer votes are necessary." There's no exclusion of the nominator, and a nomination is inherently a positive endorsement. So the nominator is generally counted as one of the three +1 votes.

Note the ambiguity: the Interest/Addition sections say "three positive (+1) votes from existing/other maintainers," which could be read as excluding the nominator. The text isn't fully consistent, so if it matters for your case, confirm with the repo's maintainers or the admin team.

What solution would you like?

Make it clear if the maintainer who is nominating others can or cannot vote.

What alternatives have you considered?

Stick with current wording

Do you have any additional context?

Add any other context or screenshots about the feature request here.

Start with RESPONSIBILITIES.md at the “Becoming a maintainer” section linked in the issue, then compare the Nomination, Interest, and Addition wording. Clarify whether the nominating maintainer may vote or counts toward the three positive votes, and consider the work done when the requirements have one unambiguous interpretation.