Replace wxEVT_GRID_HIDE_EDITOR usage with CallAfter

This simplifies the code by removing the need for a special event,
and also means the combox popup handler is no longer needed to reset
the inSetFocus flag for the closing handler.

src/generic/grid.cpp

@@ -2519,7 +2519,6 @@ wxBEGIN_EVENT_TABLE( wxGrid, wxScrolledCanvas )
     EVT_KEY_DOWN( wxGrid::OnKeyDown )
     EVT_KEY_UP( wxGrid::OnKeyUp )
     EVT_CHAR ( wxGrid::OnChar )
-    EVT_COMMAND(wxID_ANY, wxEVT_GRID_HIDE_EDITOR, wxGrid::OnHideEditor )
 wxEND_EVENT_TABLE()
 
 bool wxGrid::Create(wxWindow *parent, wxWindowID id,
@@ -7543,11 +7542,6 @@ void wxGrid::DoSaveEditControlValue()
         }
 }
 
-void wxGrid::OnHideEditor(wxCommandEvent& WXUNUSED(event))
-{
-    DisableCellEditControl();
-}
-
 //
 // ------ Grid location functions
 //  Note that all of these functions work with the logical coordinates of