Namesquatting policy: Remove references to Priority Prospects and sales

Why is this change being made?

Currently, the Namesquatting Policy page states that both paid customers and Priority Prospects can make namesquatting requests. However, Priority Prospects are specifically NOT allowed to make namesquatting requests: https://about.gitlab.com/handbook/support/priority_prospects/#support-restrictions:~:text=This%20does%20not%20include%20namesquatting%20requests

This MR removes the language from the Namesquatting page referring to Priority Prospects and lets it clearly state that only paid customers can make such requests.

Author Checklist

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• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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