Changed enums to use XXX_COUNT for the count or number of values

Fixes https://github.com/libsdl-org/SDL/issues/10763

include/SDL3/SDL_pen.h

@@ -101,7 +101,7 @@ typedef enum SDL_PenAxis
     SDL_PEN_AXIS_ROTATION,  /**< Pen barrel rotation.  Bidirectional: -180 to 179.9 (clockwise, 0 is facing up, -180.0 is facing down). */
     SDL_PEN_AXIS_SLIDER,    /**< Pen finger wheel or slider (e.g., Airbrush Pen).  Unidirectional: 0 to 1.0 */
     SDL_PEN_AXIS_TANGENTIAL_PRESSURE,    /**< Pressure from squeezing the pen ("barrel pressure"). */
-    SDL_PEN_NUM_AXES        /**< Total known pen axis types in this version of SDL. This number may grow in future releases! */
+    SDL_PEN_AXIS_COUNT       /**< Total known pen axis types in this version of SDL. This number may grow in future releases! */
 } SDL_PenAxis;
 
 /* Ends C function definitions when using C++ */