Revert "Supporting non-tensor-data write_size in planner write items. (pytorch#149434)"

This reverts commit 1442230.

Reverted pytorch#149434 on behalf of https://github.com/izaitsevfb due to breaking docs build ([comment](pytorch#149434 (comment)))

Author: pytorchmergebot

torch/distributed/checkpoint/planner.py

@@ -20,7 +20,6 @@
 __all__ = [
     "WriteItemType",
     "LoadItemType",
-    "BytesIOWriteData",
     "TensorWriteData",
     "WriteItem",
     "ReadItem",
@@ -42,11 +41,6 @@ class LoadItemType(Enum):
     BYTE_IO = auto()
 
 
-@dataclass(frozen=True)
-class BytesIOWriteData:
-    nbytes: int
-
-
 @dataclass(frozen=True)
 class TensorWriteData:
     chunk: ChunkStorageMetadata
@@ -61,9 +55,6 @@ class WriteItem:
     index: MetadataIndex
     type: WriteItemType
 
-    # Size of bytesIO data to be written.
-    bytes_io_data: Optional[BytesIOWriteData] = None
-
     # Value present if it's a tensor write
     tensor_data: Optional[TensorWriteData] = None