Remove QueryLimiting.disable for API endpoint DELETE /users/:id

What does this MR do?

This is a follow-up from the investigation in #20757 (comment 538819125). Kibana showed over the last 30 days that the endpoint has been well under 100 queries. So, Gitlab::QueryLimiting.disable is no longer needed for this API endpoint.

Does this MR meet the acceptance criteria?

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Related to #20757 (closed)