Fix typos with cspell (#6972)

wpilibc/src/main/native/include/frc/AnalogTriggerOutput.h

@@ -35,7 +35,7 @@ class AnalogTrigger;
  * / down counter or to interrupts. Because the outputs generate a pulse, they
  * cannot be read directly. To help ensure that a rollover condition is not
  * missed, there is an average rejection filter available that operates on the
- * upper 8 bits of a 12 bit number and selects the nearest outlyer of 3 samples.
+ * upper 8 bits of a 12 bit number and selects the nearest outlier of 3 samples.
  * This will reject a sample that is (due to averaging or sampling) errantly
  * between the two limits. This filter will fail if more than one sample in a
  * row is errantly in between the two limits. You may see this problem if

wpilibc/src/main/native/include/frc/Counter.h

@@ -47,8 +47,8 @@ class Counter : public CounterBase,
   /**
    * Create an instance of a counter where no sources are selected.
    *
-   * They all must be selected by calling functions to specify the upsource and
-   * the downsource independently.
+   * They all must be selected by calling functions to specify the up source and
+   * the down source independently.
    *
    * This creates a ChipObject counter and initializes status variables
    * appropriately.
@@ -148,7 +148,7 @@ class Counter : public CounterBase,
   Counter& operator=(Counter&&) = default;
 
   /**
-   * 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 use as the up source. 0-9 are on-board,
    *                10-25 are on the MXP

wpilibc/src/main/native/include/frc/SerialPort.h

@@ -34,7 +34,7 @@ class SerialPort {
     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,