[qt6][core] Don't store SignalInstance in dict for node computations

When converting the `StatusData` to a dictionary, only data attributes
should be stored in said dictionary. With Qt6, the `objectNameChanged`
signal, of type `SignalInstance`, is added to the dictionary. It needs
to be removed manually as it is not JSON-serializable. Otherwise,
the nodes cannot be computed anymore.

meshroom/core/node.py

@@ -116,8 +116,11 @@ class StatusData(BaseObject):
 
     def toDict(self):
         d = self.__dict__.copy()
-        d.pop('destroyed', None)  # skip non data attributes from BaseObject
         d["elapsedTimeStr"] = self.elapsedTimeStr
+
+        # Skip non data attributes from BaseObject
+        d.pop("destroyed", None)
+        d.pop("objectNameChanged", None)
         return d
 
     def fromDict(self, d):