[Docs] Unify lighting step descriptions (#25167)

unify lighting step descriptions and defaults across docs

docs/features/led_matrix.md

@@ -227,6 +227,8 @@ For inspiration and examples, check out the built-in effects under `quantum/led_
 #define LED_MATRIX_DEFAULT_MODE LED_MATRIX_SOLID // Sets the default mode, if none has been set
 #define LED_MATRIX_DEFAULT_VAL LED_MATRIX_MAXIMUM_BRIGHTNESS // Sets the default brightness value, if none has been set
 #define LED_MATRIX_DEFAULT_SPD 127 // Sets the default animation speed, if none has been set
+#define LED_MATRIX_VAL_STEP 8 // The value by which to increment the brightness per adjustment action
+#define LED_MATRIX_SPD_STEP 16 // The value by which to increment the animation speed per adjustment action
 #define LED_MATRIX_DEFAULT_FLAGS LED_FLAG_ALL // Sets the default LED flags, if none has been set
 #define LED_MATRIX_SPLIT { X, Y }   // (Optional) For split keyboards, the number of LEDs connected on each half. X = left, Y = Right.
                                     // If reactive effects are enabled, you also will want to enable SPLIT_TRANSPORT_MIRROR