Clarification needed on term's classification and designation's normative_status

Following pseudo YAML illustrates the problem, only relevant fields included:

```yaml
eng:
terms:
- type: expression
normative_status: (always "preferred")
designation: (taken from TERM column)
- type: expression
normative_status: (taken from SYNONYM1STATUS column)
designation: (taken from SYNONYM1 column)
- type: expression
normative_status: (taken from SYNONYM3STATUS column)
designation: (taken from SYNONYM2 column)
- type: expression
normative_status: (taken from SYNONYM3STATUS column)
designation: (taken from SYNONYM3 column)
- type: symbol
designation: (taken from SYMBOLE column)
classification: (taken from SYNONYM1STATUS column)
entry_status: (taken from STATUS column, in fact always "valid")
```

(Only relevant fields are included. Of course some spreadsheet columns may contain more than one designation, but let's skip that for simplicity.)

What I want to say is that localized concept's `classification` and `normative_status` for the 2nd term are taken from the same SYNONYM1STATUS column, and that smells like a bug. There is no TERMSTATUS column or anything like that in the spreadsheet. There is STATUS column, but it always says "Standard" and is used for `entry_status`:

https://github.com/glossarist/iev-data/blob/22a7561c76593673aa35f23987e10f4e4db440b8/lib/iev/termbase/term_builder.rb#L370-L375

----

cc @ronaldtse