Change reference to missing_data value

[Tschoun]

https://github.com/swisstopo/topo-satromo/blob/0b648c98456f19e1e39317c6ee229ff3e5e3100b/satromo_publish.py#L894C119-L894C153

The reference is hard coded to PRODUCT_VHI also if PRODUCT_VHI_HIST data should be published.