Removal equals End of Support

What does this MR do and why?

@gl-product-leadership This MR addresses the feedback captured here regarding our recent changes to deprecations, removals, and breaking changes terminology: gitlab-com/Product#4347 (comment 1045652291)

• This MR defines that a removed feature is no longer supported once removed, even if an end of support period wasn't announced at the time of deprecation.

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MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.