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/attention/attention_v1.py

@@ -75,10 +75,6 @@ class AscendAttentionBackend(AttentionBackend):
     def get_impl_cls() -> Type["AscendAttentionBackendImpl"]:
         return AscendAttentionBackendImpl
 
-    @staticmethod
-    def get_metadata_cls() -> Type["AscendMetadata"]:
-        return AscendMetadata
-
     @staticmethod
     def get_builder_cls() -> type["AscendAttentionMetadataBuilder"]:
         return AscendAttentionMetadataBuilder