Fix:embedding_model class SILICONFLOWEmbed(Base)Function reusing json (#8378)

### What problem does this PR solve?

https://github.com/infiniflow/ragflow/issues/8360

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

rag/llm/embedding_model.py

             "input": text,
             "encoding_format": "float",
         }
-        response = requests.post(self.base_url, json=payload, headers=self.headers).json()
+        response = requests.post(self.base_url, json=payload, headers=self.headers)
         try:
             res = response.json()
             return np.array(res["data"][0]["embedding"]), self.total_token_count(res)