fix(EMS-3466): no pdf - application submission - XLSX - your buyer section

[ttbarnes]

Introduction ✏️

This PR fixes an issue in the "your buyer" section of the XLSX, where the "has previous credit insurance cover with buyer" field would render even if the question/answer has not been answered.

This field should only render if the total contract value of an application is over the threshold.

Resolution ✔️

• Update XLSX_ROW_INDEXES to:
  • Not increment the DECLARATIONS title if the exporter is connected with the buyer.
  • Increment if the total contract value is over the threshold.
• Update unit tests.
• Update the mapBuyer function.
• Update mapPreviousCoverWithBuyer to only return XLSX rows if the total contract value is over the threshold.