Type must be "Policy" error when trying to import a Section to a Policy #62388668 redo

Per restart of [story 62388668](https://www.pivotaltracker.com/story/show/62388668) after [PR 770](https://github.com/reciprocity/ggrc-core/pull/770).  Template gave correct metadata headers/info, but it was still exporting with the old format, and this fixes that.