Fix #147431: Node Editor: 'Join in Named Frame' missing from menus

Operator isn't exposed in UI, now added inside Node menu.
Missed in 8ec093a2d8

Pull Request: https://projects.blender.org/blender/blender/pulls/147499

scripts/startup/bl_ui/space_node.py

@@ -443,6 +443,7 @@ class NODE_MT_node(Menu):
         layout.operator("node.join", text="Join in New Frame")
         layout.operator("node.detach", text="Remove from Frame")
         layout.operator("node.join_nodes", text="Join Group Inputs")
+        layout.operator("node.join_named")
 
         layout.separator()
         props = layout.operator("wm.call_panel", text="Rename...")