Fix confusion about representable presheaves

Thanks to Francisco García
https://stacks.math.columbia.edu/tag/03NB#comment-8391

CONTRIBUTORS

@@ -141,6 +141,7 @@ Pierre-Yves Gaillard
 Juan Sebastian Gaitan
 Lennart Galinat
 Martin Gallauer
+Francisco García
 Luis Garcia
 Xu Gao
 Toby Gee

etale-cohomology.tex

@@ -457,16 +457,17 @@ \section{Presheaves}
 
 \begin{example}
 \label{example-representable-presheaf}
-Given an object $X \in \Ob(\mathcal{C})$, we consider the functor
+Given an object $X \in \Ob(\mathcal{C})$, we consider the rule
 $$
 \begin{matrix}
-h_X : & \mathcal{C}^{opp} & \longrightarrow & \textit{Sets} \\
-& U & \longmapsto & h_X(U) = \Mor_\mathcal{C}(U, X) \\
-& V \xrightarrow{\varphi} U & \longmapsto &
-\varphi \circ - : h_X(U) \to h_X(V).
+U & \longmapsto & h_X(U) = \Mor_\mathcal{C}(U, X) \\
+V \xrightarrow{\varphi} U & \longmapsto &
+(\psi \mapsto \psi \circ \varphi) : h_X(U) \to h_X(V).
 \end{matrix}
 $$
-It is a presheaf, called the {\it representable presheaf associated to $X$.}
+This defines a functor $h_X : \mathcal{C}^{opp} \to \textit{Sets}$
+and hence a presheaf. This is called the
+{\it representable presheaf associated to $X$.}
 It is not true that representable presheaves are sheaves in every topology on
 every site.
 \end{example}