unable to set label translation.

Problem/Motivation

Unable to set label translation in view translate

Steps to reproduce

- Create view
- Add VBO field -> Select generate from xls/csv/pdf
- Select the field you want to include in export
- Save
- Edit view translate
- Select field which included to generate are not visible in VBO field.

Proposed resolution

Update schema.yml for all three xls/csv/pdf field_config -> label type to "label" instead of "string"