Remove incorrect apostrophe.
diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 8f8e165..1e4ab73 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -273,7 +273,7 @@
The *format_spec* field contains a specification of how the value should be
presented, including such details as field width, alignment, padding, decimal
-precision and so on. Each value type can define it's own "formatting
+precision and so on. Each value type can define its own "formatting
mini-language" or interpretation of the *format_spec*.
Most built-in types support a common formatting mini-language, which is