Update reusing-config.md

[HennaAbbas]

Description

A brief description of the changes.
Updated docs so that y and n are not stated as being supported as a boolean value.

Reasons

A link to a GitHub and/or JIRA issue (if applicable).
https://circleci.atlassian.net/browse/CIRCLE-34676

Content Checklist

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[rosieyohannan]

duplicate #9176 (review)