Fixup for legend mouse events in chartspace

.. when a userchart is embedded into an overview mouse events
   do not propagate in their entirety- as a result the legend
   widgets do not see MouseRelease (even though they see
   MousePress).

   So the click to show/hide when hovering over a legend item
   responds to the press not the release.

src/Charts/GenericLegend.cpp

@@ -94,7 +94,11 @@ GenericLegendItem::eventFilter(QObject *obj, QEvent *e)
     if (obj != this) return false;
 
     switch (e->type()) {
-    case QEvent::MouseButtonRelease: // for now just one event, but may do more later
+
+    // release is not propagated when embedded in chartspace
+    // so we respond to press not release events, see:
+    // https://github.com/GoldenCheetah/GoldenCheetah/issues/3992
+    case QEvent::MouseButtonPress:
         {
             if (clickable && underMouse()) {
                 enabled=!enabled;