Fix MSVC warning

Unused variable on release build

Change-Id: I2da8e1521d68d37facdf991a8943255dc01af34e
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>

src/plugins/qmldesigner/designercore/rewritertransaction.cpp

@@ -80,6 +80,7 @@ void RewriterTransaction::commit()
         if (m_activeIdentifier) {
             qDebug() << "Commit RewriterTransaction:" << m_identifier << m_identifierNumber;
             bool success = m_identifierList.removeOne(m_identifier + QByteArrayLiteral("-") + QByteArray::number(m_identifierNumber));
+            Q_UNUSED(success);
             Q_ASSERT(success);
         }
     }