Fix typos with cspell (#6972)

wpilibj/src/main/java/edu/wpi/first/wpilibj/Counter.java

@@ -90,7 +90,7 @@ public class Counter implements CounterBase, Sendable, AutoCloseable {
 
   /**
    * Create an instance of a counter where no sources are selected. Then they all must be selected
-   * by calling functions to specify the upsource and the downsource independently.
+   * by calling functions to specify the up source and the down source independently.
    *
    * <p>The counter will start counting immediately.
    */
@@ -212,7 +212,7 @@ public class Counter implements CounterBase, Sendable, AutoCloseable {
   }
 
   /**
-   * Set the upsource for the counter as a digital input channel.
+   * Set the up source for the counter as a digital input channel.
    *
    * @param channel the DIO channel to count 0-9 are on-board, 10-25 are on the MXP
    */

wpilibj/src/main/java/edu/wpi/first/wpilibj/SerialPort.java

@@ -19,7 +19,7 @@ public class SerialPort implements AutoCloseable {
     kOnboard(0),
     /** MXP (roboRIO MXP) serial port. */
     kMXP(1),
-    /** USB serial port (same as KUSB1). */
+    /** USB serial port (same as kUSB1). */
     kUSB(2),
     /** USB serial port 1. */
     kUSB1(2),

wpilibj/src/main/java/edu/wpi/first/wpilibj/drive/RobotDriveBase.java

@@ -32,7 +32,7 @@ public abstract class RobotDriveBase extends MotorSafety {
     kFrontRight(1),
     /** Rear left motor. */
     kRearLeft(2),
-    /** Reat right motor. */
+    /** Rear right motor. */
     kRearRight(3),
     /** Left motor. */
     kLeft(0),

wpilibj/src/main/java/edu/wpi/first/wpilibj/simulation/DifferentialDrivetrainSim.java

@@ -102,7 +102,7 @@ public class DifferentialDrivetrainSim {
    * @param driveMotor A {@link DCMotor} representing the drivetrain.
    * @param gearing The gearingRatio ratio of the robot, as output over input. This must be the same
    *     ratio as the ratio used to identify or create the drivetrainPlant.
-   * @param trackWidthMeters The distance between the two sides of the drivetrian. Can be found with
+   * @param trackWidthMeters The distance between the two sides of the drivetrain. Can be found with
    *     SysId.
    * @param wheelRadiusMeters The radius of the wheels on the drivetrain, in meters.
    * @param measurementStdDevs Standard deviations for measurements, in the form [x, y, heading,