[wpimath] Remove rho overload from LinearQuadraticRegulator constructors (#2687)

It was added as part of Bryson's rule described in
https://file.tavsys.net/control/controls-engineering-in-frc.pdf. It
doesn't really simplify usage though, and the same thing can be
replicated by multiplying the elements of Q by rho manually. It's easier
to do it that way, it's how 3512 has been doing controller debugging for
a while, and it's probably what other teams will do as well instead of
using the "more structured" way.

Removing these unhelpful overloads also simplifies the LQR interface.

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/statespacearm/Robot.java

@@ -78,10 +78,6 @@ public class Robot extends TimedRobot {
         // to more heavily penalize state excursion, or make the controller behave more
         // aggressively. In this example we weight position much more highly than velocity, but this
         // can be tuned to balance the two.
-        1.0, // rho balances Q and R, or velocity and voltage weights. Increasing this
-        // will penalize state excursion more heavily, while decreasing this will penalize control
-        // effort more heavily. Useful for balancing weights for systems with more states such
-        // as drivetrains.
         VecBuilder.fill(12.0), // relms. Control effort (voltage) tolerance. Decrease this to more
         // heavily penalize control effort, or make the controller less aggressive. 12 is a good
         // starting point because that is the (approximate) maximum voltage of a battery.

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/statespaceelevator/Robot.java

@@ -80,10 +80,6 @@ public class Robot extends TimedRobot {
         // heavily penalize state excursion, or make the controller behave more aggressively. In
         // this example we weight position much more highly than velocity, but this can be
         // tuned to balance the two.
-        1.0, // rho balances Q and R, or velocity and voltage weights. Increasing this
-        // will penalize state excursion more heavily, while decreasing this will penalize control
-        // effort more heavily. Useful for balancing weights for systems with more states such
-        // as drivetrains.
         VecBuilder.fill(12.0), // relms. Control effort (voltage) tolerance. Decrease this to more
         // heavily penalize control effort, or make the controller less aggressive. 12 is a good
         // starting point because that is the (approximate) maximum voltage of a battery.

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/statespaceflywheel/Robot.java

@@ -65,10 +65,6 @@ public class Robot extends TimedRobot {
         VecBuilder.fill(8.0), // qelms. Velocity error tolerance, in radians per second. Decrease
         // this to more heavily penalize state excursion, or make the controller behave more
         // aggressively.
-        1.0, // rho balances Q and R, or velocity and voltage weights. Increasing this
-        // will penalize state excursion more heavily, while decreasing this will penalize control
-        // effort more heavily. Useful for balancing weights for systems with more states such
-        // as drivetrains.
         VecBuilder.fill(12.0), // relms. Control effort (voltage) tolerance. Decrease this to more
         // heavily penalize control effort, or make the controller less aggressive. 12 is a good
         // starting point because that is the (approximate) maximum voltage of a battery.