[examples] Prepare for RobotInit deprecation by updating examples (#6623)

Co-authored-by: Tyler Veness <calcmogul@gmail.com>

developerRobot/src/main/java/frc/robot/Robot.java

@@ -11,8 +11,7 @@ public class Robot extends TimedRobot {
    * This function is run when the robot is first started up and should be used for any
    * initialization code.
    */
-  @Override
-  public void robotInit() {}
+  public Robot() {}
 
   /** This function is run once each time the robot enters autonomous mode. */
   @Override

developerRobot/src/main/native/cpp/Robot.cpp

@@ -5,11 +5,12 @@
 #include <frc/TimedRobot.h>
 
 class Robot : public frc::TimedRobot {
+ public:
   /**
    * This function is run when the robot is first started up and should be
    * used for any initialization code.
    */
-  void RobotInit() override {}
+  Robot() {}
 
   /**
    * This function is run once each time the robot enters autonomous mode