Use MergeRequests::V2ApprovalRules::UpdateService for UPDATE requests when v2 feature flag is enabled. Requirements: - Update EE::API::MergeRequestApprovalRules PUT/PATCH endpoint to check use_v2_approval_rules? flag - Call v2 UpdateService when enabled, v1 service when disabled - Add API request specs testing updates to name, approvals_required, user_ids, group_ids, remove_hidden_groups - Test validation failures, authorization failures, and feature flag toggle - Ensure response format matches v1 Reference: v2 Approval Rules POC (https://gitlab.com/gitlab-org/gitlab/-/merge_requests/222865)