typo fix

Author: avehtari

src/reference-manual/statements.qmd

@@ -726,8 +726,8 @@ if (y < -0.5 || y > 2.1) {
   target += negative_infinity();
 } else {
   target += -log_diff_exp(normal_lcdf(2.1 | 0, 1),
-}
                           normal_lcdf(-0.5 | 0, 1));
+}
 ```
 
 Because a Stan program defines a log density function, all