Reset enableFollowsExport when an export file is available to download

After exporting the follows to a csv file, the text "Processing, you'll soon be asked to download your file" remains until the whole UserSettings component is re-rendered, thus not allowing to export again. I propose to reset enableFollowsExport after a small delay when the export file is created. Since the export file is created immediately, a delay could be e.g. 2 seconds to allow the user to read the text (instantaneous text flashing might be too confusing to users).