Fix typo in schemes.tex

Thanks to Anfang
http://stacks.math.columbia.edu/tag/0356#comment-651

schemes.tex

@@ -2089,7 +2089,7 @@ \section{Reduced schemes}
 with $f(V) \subset U$ and any $g \in \mathcal{I}(U)$
 the pullback $b = f^\sharp(g) \in \Gamma(V, \mathcal{O}_Y) = B$
 maps to zero in the residue field of any $y \in V$.
-In other words $g \in \bigcap_{\mathfrak p \subset B} \mathfrak p$.
+In other words $b \in \bigcap_{\mathfrak p \subset B} \mathfrak p$.
 This implies $b = 0$ as $B$ is reduced (Lemma \ref{lemma-reduced}, and
 Algebra, Lemma \ref{algebra-lemma-Zariski-topology}).
 Hence $f$ factors through