[examples] Invert right side of drive subsystems (#3437)

The right motors of a DifferentialDrive are no longer automatically
inverted (#3340) so it needs to be done explicitly.

wpilibcExamples/src/main/cpp/examples/StateSpaceDifferentialDriveSimulation/cpp/subsystems/DriveSubsystem.cpp

@@ -14,6 +14,11 @@
 using namespace DriveConstants;
 
 DriveSubsystem::DriveSubsystem() {
+  // We need to invert one side of the drivetrain so that positive voltages
+  // result in both sides moving forward. Depending on how your robot's
+  // gearbox is constructed, you might have to invert the left side instead.
+  m_rightMotors.SetInverted(true);
+
   // Set the distance per pulse for the encoders
   m_leftEncoder.SetDistancePerPulse(kEncoderDistancePerPulse);
   m_rightEncoder.SetDistancePerPulse(kEncoderDistancePerPulse);