l -> L

THanks to Pat
https://stacks.math.columbia.edu/tag/0503#comment-9036

stacks-properties.tex

@@ -1630,7 +1630,7 @@ \section{Immersions of algebraic stacks}
 \begin{lemma}
 \label{lemma-check-immersion-covering}
 Let $f : \mathcal{X} \to \mathcal{Y}$ be a morphism of algebraic stacks.
-let $W$ be an algebraic space and let $W \to \mathcal{Y}$ be a surjective,
+Let $W$ be an algebraic space and let $W \to \mathcal{Y}$ be a surjective,
 flat morphism which is locally of finite presentation. The following
 are equivalent:
 \begin{enumerate}