Implement `allow_force_push` for protected branches in API
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### Proposal
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Allow updating the `allow_force_push` attribute of protected branch with the API.
Please note that was implemented in the UI but not API, see:
* https://gitlab.com/gitlab-org/gitlab/-/merge_requests/55261#note_591106026
* https://gitlab.com/gitlab-org/gitlab/-/merge_requests/62893#note_591114177
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issue