MENU: move chart from object submenu to main insert menu

Change-Id: If51cddafa63c79e4e7619c0c39d8f14f8eb83b25
Reviewed-on: https://gerrit.libreoffice.org/12373
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>