Fix connection to ClientDisconnected signal

[dingodoppelt]

Short description of changes

Fixes a regression in jamulusserver/clientDisconnected

CHANGELOG: Fix connection to ClientDisconnected signal

Status of this Pull Request

Ready to be merged

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[dingodoppelt]

Reintroducing this as a receiver into the connect function makes Qt::AutoConnection use Qt::QueuedConnection for connections across threads instead of Qt::DirectConnection
https://doc.qt.io/qt-6/qt.html#ConnectionType-enum