Euclidian -> Euclidean

Thanks to Théo de Oliveira Santos
https://stacks.math.columbia.edu/tag/0D8Q#comment-4591

exercises.tex

@@ -3979,7 +3979,7 @@ \section{Cohomology}
 
 \begin{exercise}
 \label{exercise-cohomology-not-zero}
-Let $X = \mathbf{R}$ with the usual Euclidian topology.
+Let $X = \mathbf{R}$ with the usual Euclidean topology.
 Using only formal properties of cohomology (functoriality
 and the long exact cohomology sequence) show that there
 exists a sheaf $\mathcal{F}$ on $X$ with nonzero $H^1(X, \mathcal{F})$.