Fix typo

Thanks to Keenan Kidwell
http://stacks.math.columbia.edu/tag/0BDY#comment-1843

coherent.tex

@@ -600,7 +600,7 @@ \section{Quasi-coherence of higher direct images}
 
 \begin{lemma}
 \label{lemma-affine-diagonal-universal-delta-functor}
-Let $X$ be a quasi-compact scheme with affine diaganal
+Let $X$ be a quasi-compact scheme with affine diagonal
 (for example if $X$ is separated). Then
 \begin{enumerate}
 \item given a quasi-coherent $\mathcal{O}_X$-module $\mathcal{F}$