Swap f and g

Thanks to Andrew
https://stacks.math.columbia.edu/tag/0C11#comment-7718

duality.tex

@@ -6342,7 +6342,7 @@ \section{Gorenstein morphisms}
 \item If $f$ and $g$ are Gorenstein, then $g \circ f$ is Gorenstein.
 \item If $g \circ f$ is Gorenstein at $x$ and $f$ is flat at $x$,
 then $f$ is Gorenstein at $x$ and $g$ is Gorenstein at $f(x)$.
-\item If $f \circ g$ is Gorenstein and $f$ is flat, then
+\item If $g \circ f$ is Gorenstein and $f$ is flat, then
 $f$ is Gorenstein and $g$ is Gorenstein at every point in
 the image of $f$.
 \end{enumerate}