Remove trailing whitespace.
diff --git a/Doc/library/mutex.rst b/Doc/library/mutex.rst
index 480c888..53656c3 100644
--- a/Doc/library/mutex.rst
+++ b/Doc/library/mutex.rst
@@ -5,7 +5,7 @@
 .. module:: mutex
    :synopsis: Lock and queue for mutual exclusion.
    :deprecated:
-   
+
 .. deprecated::
    The :mod:`mutex` module has been removed in Python 3.0.