Remove api support for param 'financial_type'

Per discussions we are not going to add support for 'financial_type' as a param in 4.3. In 4.2 'contribution_type_id' & 'contribution_type' were supported. These are aliases to 'financial_type_id' in 4.3 but we are not going to alias 'financial_type' or handle it separately as it requires separate handling.

We discussed adding support for this at the api layer & it has several advantages (e.g when the financial type is in integer it will currently be problematic) but this is not restricted or particular to this field & so reducing the amount of 'special handling' is the priority for now.

The goal is that in api v4 we will handle this better at the wrapper level & have a clearer policy on machine names vs labels.