More typo fix.

src/measure/measurable-maps/approx.tex

@@ -43,7 +43,7 @@
         d(x, I_N(x)) = \min\bracs{d(x, x_n)| 1 \le n \le N, x_n \in \mathcal{A}(x)}
         \]
 
-        In particular, $I_N(x) \to x$ as $n \to \infty$. 
+        In particular, $I_N(x) \to x$ as $N \to \infty$. 
     \end{enumerate}
 \end{lemma}
 \begin{proof}