Fix milestone associated with migrations

What does this MR do and why?

This MR updates the milestone associated with 4 migrations that were part of a security fix. Unfortunately, the security MR didn't make it into %17.0 and the migrations weren't updated at the time to reflect the new milestone. Context: https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/4023#note_1918293466

Part of #451911

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