Add mirror params to API update allow list

What does this MR do and why?

Add mirror params to API update allow list

Add the mirror_trigger_builds parameter to update_params_at_least_one_of allow list so they can be updated independently via the API. Previously, updating these parameters alone via PUT /api/v4/projects/:id returned a 400 error requiring at least one parameter from the allow list.

Closes #417081 (closed)

EE: true

Changelog: fixed

Local verification

Follow the steps in #417081 (closed) on master and see the issue is reproduced.

Follow the steps again on 417081-fix-mirror-params-api-isolation and see the field is able to be updated in isolation without error.

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How to set up and validate locally

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Related to #417081 (closed)