QMakeStep: Fix compilation warning

Remove unused variable.

Change-Id: I8e060a8569edfa34483497188d480e624fc2c5fe
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>

src/plugins/qt4projectmanager/qmakestep.cpp

@@ -704,8 +704,6 @@ void QMakeStepConfigWidget::updateSummaryLabel()
 void QMakeStepConfigWidget::updateQmlDebuggingOption()
 {
     m_ui->qmlDebuggingLibraryCheckBox->setEnabled(m_step->isQmlDebuggingLibrarySupported());
-
-    QtSupport::BaseQtVersion *qtVersion = m_step->qt4BuildConfiguration()->qtVersion();
     m_ui->debuggingLibraryLabel->setText(tr("Enable QML debugging:"));
 
     QString warningText;