Fix flaky test.

This test failed on master because it saw "Loading" and did not wait.

lms/djangoapps/instructor/features/data_download.py

@@ -18,7 +18,7 @@ def find_student_profile_table(step):  # pylint: disable=unused-argument
     world.wait_for_visible('#data-student-profiles-table')
 
     # Wait for the data table to be populated
-    world.wait_for(lambda _: world.css_text('#data-student-profiles-table') not in [u'', u'Loading...'])
+    world.wait_for(lambda _: world.css_text('#data-student-profiles-table') not in [u'', u'Loading'])
 
     if world.role == 'instructor':
         expected_data = [