Remove spurious period.

Doc/lib/libstdtypes.tex

@@ -410,7 +410,7 @@ item tuple must have a trailing comma, e.g., \code{(d,)}.
 
 Buffer objects are not directly supported by Python syntax, but can be
 created by calling the builtin function
-\function{buffer()}.\bifuncindex{buffer}.  They don't support
+\function{buffer()}.\bifuncindex{buffer}  They don't support
 concatenation or repetition.
 \obindex{buffer}