Remove accidental not (#4448)

We want tworkers to skip the function, not non-tworkers.

src/clusterfuzz/_internal/bot/tasks/commands.py

@@ -80,7 +80,7 @@ class AlreadyRunningError(Error):
 def cleanup_task_state():
   """Cleans state before and after a task is executed."""
   # Cleanup stale processes.
-  if not environment.is_tworker():
+  if environment.is_tworker():
     return
   process_handler.cleanup_stale_processes()