Don't double mirror groups.

Also removes previous fix, which had side-effects.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/8121

Fixes https://gitlab.com/kicad/code/kicad/-/issues/20465

(cherry picked from commit 3f85071f91)

pcbnew/pcb_group.cpp

@@ -137,12 +137,7 @@ PCB_GROUP* getNestedGroup( BOARD_ITEM* aItem, PCB_GROUP* aScope, bool isFootprin
         return nullptr;
 
     while( group && group->GetParentGroup() && group->GetParentGroup() != aScope )
-    {
-        if( group->GetParent()->Type() == PCB_FOOTPRINT_T && isFootprintEditor )
-            break;
-
         group = group->GetParentGroup();
-    }
 
     return group;
 }

pcbnew/tools/edit_tool.cpp

@@ -2243,25 +2243,7 @@ int EDIT_TOOL::Mirror( const TOOL_EVENT& aEvent )
     FLIP_DIRECTION flipDirection = aEvent.IsAction( &PCB_ACTIONS::mirrorV ) ? FLIP_DIRECTION::TOP_BOTTOM
                                                                             : FLIP_DIRECTION::LEFT_RIGHT;
 
-    std::vector<EDA_ITEM*> items;
-
     for( EDA_ITEM* item : selection )
-    {
-        if( item->Type() == PCB_GROUP_T )
-        {
-            static_cast<PCB_GROUP*>( item )->RunOnDescendants(
-                    [&]( BOARD_ITEM* descendant )
-                    {
-                        items.push_back( descendant );
-                    } );
-        }
-        else
-        {
-            items.push_back( item );
-        }
-    }
-
-    for( EDA_ITEM* item : items )
     {
         if( !item->IsType( MirrorableItems ) )
             continue;