correct mention of old course ID in description of bulk email django tool

lms/djangoapps/bulk_email/admin.py

@@ -70,7 +70,7 @@ class CourseAuthorizationAdmin(admin.ModelAdmin):
         (None, {
             'fields': ('course_id', 'email_enabled'),
             'description': '''
-Enter a course id in the following form: Org/Course/CourseRun, eg MITx/6.002x/2012_Fall
+Enter a course id in the following form: course-v1:Org+CourseNumber+CourseRun, eg course-v1:edX+DemoX+Demo_Course
 Do not enter leading or trailing slashes. There is no need to surround the course ID with quotes.
 Validation will be performed on the course name, and if it is invalid, an error message will display.