Rename RungeKutta to RungeKuttaU

This could be done with lambda instead, but we'll leave it.  I need a
variant where time gets passed in and this was using that call
signature.  I'd rather rename this one.

Change-Id: Ic8e473db599528e17efc0dc30a734679237a5cca
diff --git a/y2018/control_loops/superstructure/arm/dynamics.h b/y2018/control_loops/superstructure/arm/dynamics.h
index cdbd6fe..b1ebc97 100644
--- a/y2018/control_loops/superstructure/arm/dynamics.h
+++ b/y2018/control_loops/superstructure/arm/dynamics.h
@@ -169,15 +169,15 @@
   static const ::Eigen::Matrix<double, 4, 1> UnboundedDiscreteDynamics(
       const ::Eigen::Matrix<double, 4, 1> &X,
       const ::Eigen::Matrix<double, 2, 1> &U, double dt) {
-    return ::frc971::control_loops::RungeKutta(Dynamics::Acceleration, X, U,
-                                               dt);
+    return ::frc971::control_loops::RungeKuttaU(Dynamics::Acceleration, X, U,
+                                                dt);
   }
 
   static const ::Eigen::Matrix<double, 6, 1> UnboundedEKFDiscreteDynamics(
       const ::Eigen::Matrix<double, 6, 1> &X,
       const ::Eigen::Matrix<double, 2, 1> &U, double dt) {
-    return ::frc971::control_loops::RungeKutta(Dynamics::EKFAcceleration, X, U,
-                                               dt);
+    return ::frc971::control_loops::RungeKuttaU(Dynamics::EKFAcceleration, X, U,
+                                                dt);
   }
 };