fix: late joiners would be displayed as selected [MTTB-4]

[fernando-cortez]

Description

This PR fixes the issue where a previously connected client's party HUD slot would be displayed as selected (green) when a new client would join and assume that slot. The state is now cleared on an ally's disconnected callback.

To validate (min steps):

• Have one player host
• Connect a client
• Have host select (target) client
• Have client disconnect
• Reconnect client

Expected: PartyHUD state for client should be unselected

Issue Number(s)

MTTB-4

Contribution checklist

• [ N/A ] Tests have been added for boss room and/or utilities pack
• Release notes have been added to the project changelog file and/or package changelog file
• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• JIRA ticket ID is in the PR title or at least one commit message
• Include the ticket ID number within the body message of the PR to create a hyperlink
• [ N/A ] An Index entry has been added in readme.md if applicable

[FabianStoll]

Works as described