Fixed regex incident.

src/topology/main/normal.tex

@@ -23,7 +23,7 @@
         \begin{enumerate}
             \item[(a)] $U_1 = B^c$.
             \item[(b)] For any $p, q \in \rational \cap [0, 1]$ with $p < q$, $\overline{U_p} \subset U_q$.
-        \end\{enumerate\}
+        \end{enumerate}
 
         \item There exists $f \in C(X; [0, 1])$ with $f|_A = 0$ and $f|_B = 1$.
     \end{enumerate}