Fix typo: Sixt -> Sixth

Author: delirious-lettuce

examples/progress-bar/many-parallel-tasks.py

@@ -24,7 +24,7 @@ def run_task(label, total, sleep_time):
  threading.Thread(target=run_task, args=('Third task', 8, 3)),
  threading.Thread(target=run_task, args=('Fourth task', 200, .1)),
  threading.Thread(target=run_task, args=('Fifth task', 40, .2)),
- threading.Thread(target=run_task, args=('Sixt task', 220, .1)),
+ threading.Thread(target=run_task, args=('Sixth task', 220, .1)),
  threading.Thread(target=run_task, args=('Seventh task', 85, .05)),
  threading.Thread(target=run_task, args=('Eight task', 200, .05)),
  ]