Fix some error messages
Created by: ghost
Fixed small errors shown by terminal warnings since 3d0bd1a:
ERROR: emit_signal: Error calling method from signal 'keying_changed': 'EditorNode::_update_keying': Expected 0 arguments.
At: core/object.cpp:1210.
I have removed the SpatialEditor::_update_selection because it was always empty.
ERROR: emit_signal: Error calling method from signal 'selection_changed': 'SpatialEditor::_update_selection': Method not found.
At: core/object.cpp:1210.