fix: can not sign out if not signed in yet COMPASS-7787

[alenakhineika]

Description

Clean up Aatlas signing store, so it properly sets the 'unauthenticated' state after a user clicks the "Disconnect" button on the Setting page. Otherwise the "Log in with Atlas" -> "Disconnect" -> "Log in with Atlas" flow doesn't trigger the OIDC auth and a further "Disconnect" throws the "Error: Can't sign out if not signed in yet" error.

Checklist

• [x] New tests and/or benchmarks are included
• [ ] Documentation is changed or added
• [ ] I have signed the MongoDB Contributor License Agreement (https://www.mongodb.com/legal/contributor-agreement)

Motivation and Context

• [x] Bugfix
• [ ] New feature
• [ ] Dependency update
• [ ] Misc

Types of changes

• [ ] Backport Needed
• [x] Patch (non-breaking change which fixes an issue)
• [ ] Minor (non-breaking change which adds functionality)
• [ ] Major (fix or feature that would cause existing functionality to change)