Fix: Entering node group via icon after exiting it via ctrl+tab broken

This is because the `NODE_OT_group_edit` operator reuses the last value
of the `Exit` property and once this is set it would always try to pop
(instead of push [which is what we want from the icon]) the nodegroup.

Callers of the operator set `Exit` explicitly elsewhere (just not
from node drawing -- where the way it is called [via a more general
callback] makes it difficult to set operator properties from there).

Solve by not saving the property for following usages (flag
`PROP_SKIP_SAVE`).

Fixes #117530.

Pull Request: https://projects.blender.org/blender/blender/pulls/117542

source/blender/editors/space_node/node_group.cc

@@ -207,7 +207,8 @@ void NODE_OT_group_edit(wmOperatorType *ot)
   /* flags */
   ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 
-  RNA_def_boolean(ot->srna, "exit", false, "Exit", "");
+  PropertyRNA *prop = RNA_def_boolean(ot->srna, "exit", false, "Exit", "");
+  RNA_def_property_flag(prop, PROP_SKIP_SAVE);
 }
 
 /** \} */