Fix live coding example.

Thanks to @nicoder for the suggestion.

Fixes #206

Author: samaaron

etc/doc/tutorial/09.1-Live-Coding-Fundamentals.md

@@ -65,7 +65,7 @@ a chord:
 ```
 define :my_loop do
   use_synth :tb303
-  play choose(chord(:e3, :minor)), release: 0.3
+  play chord(:e3, :minor), release: 0.3
   sleep 0.5
 end
 ```