Update json_kv_impl.py

There is no delete function in chunks_vdb and text_chunks in lines 1300-1302 of the lightrag.py file：
if chunk_ids:
await self.chunks_vdb.delete(chunk_ids)
await self.text_chunks.delete(chunk_ids)

lightrag/kg/json_kv_impl.py

@@ -47,3 +47,8 @@ class JsonKVStorage(BaseKVStorage):
 
     async def drop(self) -> None:
         self._data = {}
+    
+    async def delete(self, ids: list[str]) -> None:
+        for doc_id in ids:
+            self._data.pop(doc_id, None)
+        await self.index_done_callback()