Handle case when team admin revokes their admin role or removes themself from a team

[taras-yemets]

Follow-up on https://github.com/sourcegraph/sourcegraph/issues/63240

https://github.com/sourcegraph/sourcegraph/pull/63388 adds confirmation modals for the actions of revoking admin privileges and removing users on the “/cody/team/manage” page. These modals are generic, giving the impression that the actions pertain to another user (e.g., one admin revoking another admin or removing another user).

To address this, we may want to:
1. Provide specific confirmation text for scenarios where an admin user is revoking their own admin role or removing themselves from the team.
2. Add an indicator to the team members list to identify the current user.