Typo repair.

Doc/tut/tut.tex

@@ -5486,7 +5486,7 @@ While pathological cases do exist, for most casual use of
 floating-point arithmetic you'll see the result you expect in the end
 if you simply round the display of your final results to the number of
 decimal digits you expect.  \function{str()} usually suffices, and for
-finer control see the discussion of Pythons's \code{\%} format
+finer control see the discussion of Python's \code{\%} format
 operator: the \code{\%g}, \code{\%f} and \code{\%e} format codes
 supply flexible and easy ways to round float results for display.