CLC-4488 - eGrades Export Tool: Refactor Javascript to link to eGrades Export tool installed in 'Official Courses' sub-account

https://jira.ets.berkeley.edu/jira/browse/CLC-4488
@redconfetti would recommend doing an extra check here.

```
officialCourseResponse && officialCourseResponse.isOfficialCourse === true
```