Don't drop selection on an undo/redo.

We want to be able to restore it back to the way it was.

Fixes https://gitlab.com/kicad/code/kicad/issues/5356

pcbnew/tools/selection_tool.cpp

@@ -317,11 +317,6 @@ int SELECTION_TOOL::Main( const TOOL_EVENT& aEvent )
                 m_toolMgr->RunAction( PCB_ACTIONS::clearHighlight );
         }
 
-        else if( evt->Action() == TA_UNDO_REDO_PRE )
-        {
-            ClearSelection();
-        }
-
         else
             evt->SetPassEvent();
     }