[misc] clean up get_metadata_cls (#4276)

Follow up #4087 to remove get_metadata_cls 
- vLLM version: v0.11.0
- vLLM main:
vllm-project/vllm@2918c1b

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

Author: wangxiyuan

tests/ut/torchair/test_torchair_sfa.py

@@ -16,10 +16,6 @@ def test_get_name(self):
         self.assertEqual(AscendSFATorchairBackend.get_name(),
                          "ASCEND_SFA_TORCHAIR")
 
-    def test_get_metadata_cls(self):
-        self.assertEqual(AscendSFATorchairBackend.get_metadata_cls(),
-                         AscendSFATorchairMetadata)
-
     def test_get_builder_cls(self):
         self.assertEqual(AscendSFATorchairBackend.get_builder_cls(),
                          AscendSFATorchairMetadataBuilder)