Fixed regex incident.

src/topology/main/hausdorff.tex

@@ -12,7 +12,7 @@
         \item Every filter in $X$ converges to at most one point.
         \item For any index set $I$, the diagonal $\Delta$ is closed in $X^I$.
         \item The diagonal $\Delta$ is closed in $X \times X$.
-    \end\{enumerate\}
+    \end{enumerate}
 
     If the above holds, then $X$ is a \textbf{T2/Hausdorff} space.
 \end{definition}