fix: unused import

Author: lorenzocesconetto

src/mcp/shared/session.py

@@ -8,7 +8,7 @@
 import anyio
 import httpx
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
-from pydantic import BaseModel, ValidationError
+from pydantic import BaseModel
 from typing_extensions import Self
 
 from mcp.shared.exceptions import McpError