Select correct dropdown option when role upgrade canceled

What does this MR do and why?

Related to #417073 (closed)

Fixes when you hit cancel in the overage modal, expanding the dropdown still had the canceled role option selected.

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Open up the rails console rails c and enable the show_overage_on_role_promotion flag (Feature.enable(:show_overage_on_role_promotion))
• Navigate to the project members page for a project that's linked to a subscription (ex: gitlab-org/gitlab-shell/-/project_members)
• Change the Max role value, the modal should appear
• Click off of the modal or click "Back"
• Open the dropdown
• Verify selected role is correct and not the upgraded role

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.