Add logic to Projects::AllBranchesRule::MergeRequestApprovalSetting to load `prevent_committer_approval`
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In https://gitlab.com/gitlab-org/gitlab/-/issues/504615+ we created a new table and renamed some of the attributes to better suit the new system.
`merge_requests_disable_committers_approval` has been renamed to `prevent_committer_approval` so we need to create a method in `Projects::AllBranchesRule::MergeRequestApprovalSetting` to fetch `project.merge_requests_disable_committers_approval`
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