DOC: Fixes error in sample script provided in 'Getting started' section

set_trace is directly imported by qdb.set_traced was used in the main()
function.

Author: Conor McGee

README.md

@@ -65,7 +65,7 @@ def f():
 
 
 def main():
-    qdb.set_trace(
+    set_trace(
         uuid='qdb',
         host='localhost',
         port=8001,