Fix typo.

Doc/lib/libcodecs.tex

@@ -237,7 +237,7 @@ any other keyword argument) is passed through to the incremental encoder.
 \begin{funcdesc}{iterdecode}{iterable, encoding\optional{, errors}}
 Uses an incremental decoder to iteratively decode the input provided by
 \var{iterable}. This function is a generator. \var{errors} (as well as
-any other keyword argument) is passed through to the incremental encoder.
+any other keyword argument) is passed through to the incremental decoder.
 \versionadded{2.5}
 \end{funcdesc}