doc: Add non-male interviewers in Enablement

Why is this change being made?

Add requirement for at least one interviewer to be non-male.

This aligns with Support's https://about.gitlab.com/handbook/support/managers/hiring.html#behavioural-panel-interview introduced in !74897 (merged).

The goal is to help surface biases, include diversity of thought in feedback, and represent this facet of GitLab's culture and commitment towards candidates.

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