Remove temporary footprint from pcb group before deletion

Bounding box computation uses a temporary footprint, but the clone
operation keeps the group information. We can't delete a footprint if it
has group information, so just delete the group information.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/14909

(Cherry-picked from b8e9544828)

pcbnew/footprint.cpp

@@ -801,7 +801,9 @@ BOX2I FOOTPRINT::GetFpPadsLocalBbox() const
     for( PAD* pad : dummy.Pads() )
         bbox.Merge( pad->GetBoundingBox() );
 
+    // Remove the parent and the group from the dummy footprint before deletion
     dummy.SetParent( nullptr );
+    dummy.SetParentGroup( nullptr );
 
     return bbox;
 }