fix security.md location & docs

[hunterschep]

This update makes minor tweaks in conjunction with today's meeting

• move security.md up to the top level as it will be recognized as one of the reserved names and display under the site policy correctly
• remove old links to the security page and update the current links to the new location

[changeset-bot[bot]]

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Latest commit: 4f9ffdd9ed79ff1d4ab1f846f537cdff889e0fb1

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