Use correct dewarp math on jevois.

Change-Id: If637ac28c3d62523fd59b2c4de48e55824e2fb33
diff --git a/y2019/vision/target_finder.cc b/y2019/vision/target_finder.cc
index 2cd5130..a56d82c 100644
--- a/y2019/vision/target_finder.cc
+++ b/y2019/vision/target_finder.cc
@@ -71,8 +71,7 @@
   double y = y0;
   for (int i = 0; i < iterations; i++) {
     const double r_sqr = x * x + y * y;
-    const double coeff =
-        1.0 + r_sqr * (k_1 + k_2 * r_sqr * (1.0 + k_3 * r_sqr));
+    const double coeff = 1.0 + r_sqr * (k_1 + r_sqr * (k_2 + r_sqr * (k_3)));
     x = x0 / coeff;
     y = y0 / coeff;
   }