Remove redundant footnote (#181)
It was accidentally added in cc79837.
diff --git a/Doc/tutorial/datastructures.rst b/Doc/tutorial/datastructures.rst
index 0e5891a..916da4a 100644
--- a/Doc/tutorial/datastructures.rst
+++ b/Doc/tutorial/datastructures.rst
@@ -107,7 +107,7 @@
You might have noticed that methods like ``insert``, ``remove`` or ``sort`` that
only modify the list have no return value printed -- they return the default
-``None``. [1]_ This is a design principle for all mutable data structures in
+``None``. This is a design principle for all mutable data structures in
Python.