test: fix coverage pragmas

Author: Ar-maan05

src/mcp/shared/session.py

@@ -472,7 +472,7 @@ async def _handle_session_message(message: SessionMessage) -> None:
                     try:
                         await stream.send(JSONRPCError(jsonrpc="2.0", id=id, error=error))
                         await stream.aclose()
-                    except Exception:  # pragma: no cover
+                    except Exception:
                         # Stream might already be closed
                         pass
                 self._response_streams.clear()