Make arm spline definition a ton easier

Remove all the redundant intermediate variables.

Change-Id: I1e1d93b8a4363f3498775a0eead3d14ae190e77a
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/y2023/joystick_reader.cc b/y2023/joystick_reader.cc
index 5cb148c..193d3b7 100644
--- a/y2023/joystick_reader.cc
+++ b/y2023/joystick_reader.cc
@@ -155,7 +155,7 @@
 
     double wrist_goal = 0.0;
     RollerGoal roller_goal = RollerGoal::IDLE;
-    arm_goal_position_ = arm::NeutralPosIndex();
+    arm_goal_position_ = arm::NeutralIndex();
     std::optional<double> score_wrist_goal = std::nullopt;
 
     if (data.IsPressed(kGroundPickupConeUp) || data.IsPressed(kHPConePickup)) {