Change 'video' to 'audio' in transcript description

Updated the description of the audio clip in the transcript.

Author: rmiller78

app/views/primary_source_sets/obama-rise/1-16-st7dr2pt8z.md

@@ -13,7 +13,7 @@ In 2004, four years before he became the president of the United States, Barack
 
 <b>Focus 580; Talk to the Candidates with Barack Obama</b>
 <b>| WILL Illinois Public Media (Television station : Urbana, IL.) | February 16, 2004 </b>
-<i>This video clip and associated transcript appear from 2:28 - 6:40 in the full record.</i>
+<i>This audio clip and associated transcript appear from 2:28 - 6:40 in the full record.</i>
 
 ## Teachingtips