Debugger: Fix DebuggerKitConfigWidget::onDebuggerRemoved() implementation

DebuggerKitConfigWidget::onDebuggerRemoved() is erroneously calling
updateComboBox() with the id of the removed item, which resets debugger input
for all other existing kits that are using valid exiting debuggers.

Task-number: QTCREATORBUG-10484

Change-Id: Ib989fdccfc87386785c7ca95ded860499ac2b98c
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>