Remove duplication.
diff --git a/Demo/threads/sync.py b/Demo/threads/sync.py
index 843767a..a344abe 100644
--- a/Demo/threads/sync.py
+++ b/Demo/threads/sync.py
@@ -265,7 +265,7 @@
# intervening. If there are other threads waiting to write, they
# are allowed to proceed only if the current thread calls
# .read_out; threads waiting to read are only allowed to proceed
-# if there are are no threads waiting to write. (This is a
+# if there are no threads waiting to write. (This is a
# weakness of the interface!)
import thread