Fix multiple Java warnings (#6201)

wpilibj/src/test/java/edu/wpi/first/wpilibj/drive/DifferentialDriveTest.java

@@ -9,6 +9,7 @@ import static org.junit.jupiter.api.Assertions.assertEquals;
 import edu.wpi.first.wpilibj.motorcontrol.MockPWMMotorController;
 import org.junit.jupiter.api.Test;
 
+@SuppressWarnings("resource")
 class DifferentialDriveTest {
   @Test
   void testArcadeDriveIK() {

wpilibj/src/test/java/edu/wpi/first/wpilibj/drive/MecanumDriveTest.java

@@ -10,6 +10,7 @@ import edu.wpi.first.math.geometry.Rotation2d;
 import edu.wpi.first.wpilibj.motorcontrol.MockPWMMotorController;
 import org.junit.jupiter.api.Test;
 
+@SuppressWarnings("resource")
 class MecanumDriveTest {
   @Test
   void testCartesianIK() {

wpilibj/src/test/java/edu/wpi/first/wpilibj/simulation/ElevatorSimTest.java

@@ -22,6 +22,7 @@ class ElevatorSimTest {
   void testStateSpaceSimWithElevator() {
     RoboRioSim.resetData();
 
+    @SuppressWarnings("resource")
     var controller = new PIDController(10, 0, 0);
 
     var sim =