Legal API - IA should not use business object in filing

**Describe the bug in current situation**
IA validation is depending on `business/legalType` property. Even though it is working now it is against schema. To get legalType we can use `namerequest/legalType`. Make sure business object not used in case of IA

**Expected behaviour**
Business object is not used in case of IA

**TO DO**
- [ ] Investigate what needs to be done and document it in this ticket
- [ ] Update validator to **not** validate the legal type using the business object
- [ ] Ignore the business object even if it is there

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- UI work (to be completed in ____)
- Backend work to (be completed in ____ )

Start by locating the IA filing validator and trace how it reads legalType from business/legalType versus namerequest/legalType. Document the required change in this issue, then ensure the validator ignores business even when present and add or update the relevant validation coverage; no file or test is named in the payload.

Written by the indexing model from the issue text.