[Course Import/Export] Change Title of Course Export Download link

Problem statement:

The course export function generates an oblique name that does not indicate how to obtain the course export package. Currently it states "Course export from 5 minutes ago" WCAG 2.1 Success Criterion 2.4. 4 Link Purpose (In Context) (Level A) states The purpose of each link can be determined from the link text alone or from the link text together with its programmatically determined link context, except where the purpose of the link would be ambiguous to users in general.

Proposed solution:

Modify the link descriptor to indicate the purpose of the link eg "The course export from 5 minutes ago is available to download here"

User role(s):

admin,instructor,designer