qmlplugindump: Fix handling of implicit signals

Change I70affc450 added inverted logic.

Change-Id: I6cb25d3881a0487545a3eeac289a34fedcc21d8f
Reviewed-by: Christian Kamm <christian.d.kamm@nokia.com>

tools/qmlplugindump/main.cpp

@@ -473,7 +473,7 @@ private:
                 && !meth.revision()
                 && meth.methodType() == QMetaMethod::Signal
                 && meth.parameterNames().isEmpty()
-                && typeName != QLatin1String("void")) {
+                && typeName == QLatin1String("void")) {
             // don't mention implicit signals
             return;
         }