remove get_metadata_cls (#4087)

remove get_metadata_cls. It's only used for V0 engine and has been removed from vLLM already.

- vLLM version: v0.11.0
- vLLM main:
83f478bb19

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm_ascend/torchair/torchair_attention.py

@@ -55,10 +55,6 @@ class AscendAttentionTorchairBackend(AscendAttentionBackend):
     def get_impl_cls() -> Type["AscendAttentionTorchairBackendImpl"]:
         return AscendAttentionTorchairBackendImpl
 
-    @staticmethod
-    def get_metadata_cls() -> Type["AscendTorchairMetadata"]:
-        return AscendTorchairMetadata
-
     @staticmethod
     def get_builder_cls() -> type["AscendAttentionTorchairMetadataBuilder"]:
         return AscendAttentionTorchairMetadataBuilder