Fix grammatical error in csv docs.
Reported by Nat Dunn on docs@
diff --git a/Doc/library/csv.rst b/Doc/library/csv.rst
index 1f5ae65..d3d505e 100644
--- a/Doc/library/csv.rst
+++ b/Doc/library/csv.rst
@@ -338,7 +338,7 @@
.. attribute:: Dialect.doublequote
- Controls how instances of *quotechar* appearing inside a field should be
+ Controls how instances of *quotechar* appearing inside a field should
themselves be quoted. When :const:`True`, the character is doubled. When
:const:`False`, the *escapechar* is used as a prefix to the *quotechar*. It
defaults to :const:`True`.