Fix typo.

Author: ChristianSi

README.md

@@ -322,8 +322,8 @@ Any Unicode character may be escaped with the `\uXXXX` or `\UXXXXXXXX` forms.
 The escape codes must be valid Unicode [scalar
 values](http://unicode.org/glossary/#unicode_scalar_value).
 
-All other escape sequences not listed above are reserved; if they are used used,
-TOML should produce an error.
+All other escape sequences not listed above are reserved; if they are used, TOML
+should produce an error.
 
 Sometimes you need to express passages of text (e.g. translation files) or would
 like to break up a very long string into multiple lines. TOML makes this easy.