Undo/Redo: remove unused EXCHANGE_T type

eeschema/schematic_undo_redo.cpp

@@ -234,7 +234,6 @@ void SCH_EDIT_FRAME::SaveCopyInUndoList( const PICKED_ITEMS_LIST& aItemsList,
 
         case UNDO_REDO::NEWITEM:
         case UNDO_REDO::DELETED:
-        case UNDO_REDO::EXCHANGE_T:
         case UNDO_REDO::PAGESETTINGS:
             break;
 
@@ -359,12 +358,6 @@ void SCH_EDIT_FRAME::PutDataInPreviousState( PICKED_ITEMS_LIST* aList )
 
                 break;
 
-            case UNDO_REDO::EXCHANGE_T:
-                aList->SetPickedItem( alt_item, ii );
-                aList->SetPickedItemLink( item, ii );
-                item = alt_item;
-                break;
-
             default:
                 wxFAIL_MSG( wxString::Format( wxT( "Unknown undo/redo command %d" ),
                                               aList->GetPickedItemStatus( ii ) ) );

include/undo_redo_container.h

@@ -65,8 +65,6 @@ enum class UNDO_REDO {
     LIBEDIT,            // Specific to the component editor (symbol_editor creates a full copy
                         // of the current component when changed)
     LIB_RENAME,         // As LIBEDIT, but old copy should be removed from library
-    EXCHANGE_T,         // Use for changing the schematic text type where swapping
-                        // data structure is insufficient to restore the change.
     DRILLORIGIN,        // origin changed (like CHANGED, contains the origin and a copy)
     GRIDORIGIN,         // origin changed (like CHANGED, contains the origin and a copy)
     PAGESETTINGS,       // page settings or title block changes