[Doc] Fix typo in docstring (#527)

mmengine/structures/instance_data.py

@@ -16,7 +16,7 @@ IndexType = Union[str, slice, int, list, torch.LongTensor,
 # Modified from
 # https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/data_structures/instance_data.py # noqa
 class InstanceData(BaseDataElement):
-    """Data structure for instance-level annnotations or predictions.
+    """Data structure for instance-level annotations or predictions.
 
     Subclass of :class:`BaseDataElement`. All value in `data_fields`
     should have the same length. This design refer to

mmengine/structures/label_data.py

@@ -6,7 +6,7 @@ from .base_data_element import BaseDataElement
 
 
 class LabelData(BaseDataElement):
-    """Data structure for label-level annnotations or predictions."""
+    """Data structure for label-level annotations or predictions."""
 
     @staticmethod
     def onehot_to_label(onehot: torch.Tensor) -> torch.Tensor:

mmengine/structures/pixel_data.py

@@ -9,7 +9,7 @@ from .base_data_element import BaseDataElement
 
 
 class PixelData(BaseDataElement):
-    """Data structure for pixel-level annnotations or predictions.
+    """Data structure for pixel-level annotations or predictions.
 
     All data items in ``data_fields`` of ``PixelData`` meet the following
     requirements: