Add Switchboard maintainer roles

Why is this change being made?

Expand switchboard team members' data to include the maintainership for the Switchboard project https://gitlab.com/gitlab-com/gl-infra/gitlab-dedicated/switchboard.

This MR adds maintainership to:

• Andrey Ruzmanov => backend, frontend
• Jose Vargas => frontend
• Sean Arnold => backend, frontend
• Ruben Pereira => backend
• Mayra Cabrera => backend

Contributes to !126362 (merged)

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
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  • The when to get approval handbook section explains the workflow in more detail
• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
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