Fix docstring of pyramid keys (#2391)

Author: smitlg

keras_cv/models/object_detection/yolo_v8/yolo_v8_detector.py

@@ -331,7 +331,7 @@ class YOLOV8Detector(Task):
 
     Args:
         backbone: `keras.Model`, must implement the `pyramid_level_inputs`
-            property with keys "P2", "P3", and "P4" and layer names as values.
+            property with keys "P3", "P4", and "P5" and layer names as values.
             A sensible backbone to use is the `keras_cv.models.YOLOV8Backbone`.
         num_classes: integer, the number of classes in your dataset excluding the
             background class. Classes should be represented by integers in the