Add Object Tool: remove from experimental

Based on feedback from @dbystedt, include this in 2.92
with some updates (coming next).

release/scripts/startup/bl_ui/space_userpref.py

@@ -2236,7 +2236,6 @@ class USERPREF_PT_experimental_new_features(ExperimentalPanel, Panel):
                 ({"property": "use_sculpt_vertex_colors"}, "T71947"),
                 ({"property": "use_switch_object_operator"}, "T80402"),
                 ({"property": "use_sculpt_tools_tilt"}, "T82877"),
-                ({"property": "use_object_add_tool"}, "T57210"),
                 ({"property": "use_asset_browser"}, ("project/profile/124/", "Milestone 1")),
             ),
         )