Add period

THanks to Matthieu Romagny
https://stacks.math.columbia.edu/tag/0AY2#comment-6273

divisors.tex

@@ -1925,7 +1925,7 @@ \section{Reflexive modules}
 \begin{enumerate}
 \item If $\mathcal{F}$ is reflexive, then $\mathcal{F}$ is torsion free.
 \item The map $j : \mathcal{F} \longrightarrow \mathcal{F}^{**}$
-is injective if and only if $\mathcal{F}$ is torsion free
+is injective if and only if $\mathcal{F}$ is torsion free.
 \end{enumerate}
 \end{lemma}