Explain where we use Hausdorff property

Thanks to Kiran Kedlaya
https://stacks.math.columbia.edu/tag/09V2#comment-4856

cohomology.tex

@@ -2645,6 +2645,7 @@ \section{Cohomology on Hausdorff quasi-compact spaces}
 such that $h_{i_0 \ldots i_n}|_{W_{i_0 \ldots i_n, k}}$
 lifts to a section of $\mathcal{G}$ over $W_{i_0 \ldots i_n, k}$.
 By Topology, Lemma \ref{topology-lemma-refine-covering}
+(this is where we use the assumption that $X$ is hausdorff and quasi-compact)
 we can choose an open covering $\mathcal{V} : X = \bigcup_{j \in J} V_j$
 and $\alpha : J \to I$ such that $V_j \subset U_{\alpha(j)}$
 (it is a refinement) and such that for all $j_0, \ldots, j_n \in J$