Don't force wxAuiToolBar size to be less than its parent

This results in the toolbar being too small to show any items in it
in wxGTK and wxOSX, because the parent window size is still the default
small one and not the actual size it will be when shown, when the size
of the toolbar is first set.

And it seems completely unnecessary to do this anyhow, as toolbar is
resized by wxAuiManager in any case.

Closes #18218.

include/wx/aui/auibar.h

@@ -618,12 +618,6 @@ protected:
     wxSize GetLabelSize(const wxString& label);
     wxAuiToolBarItem* FindToolByPositionWithPacking(wxCoord x, wxCoord y) const;
 
-    void DoSetSize(int x,
-                   int y,
-                   int width,
-                   int height,
-                   int sizeFlags = wxSIZE_AUTO) wxOVERRIDE;
-
 protected: // handlers
 
     void OnSize(wxSizeEvent& evt);