the flashblock websocket endpoint seems broken

Hi, Op team:
I tried to connect to wss://op-mainnet-fb-ws-pub.optimism.io/ws, it report: handshake failed.
How can I avoid such issue or any guide to use the websocket properly?

Start by reproducing the handshake failure against wss://op-mainnet-fb-ws-pub.optimism.io/ws and check the repository for the Flashblocks WebSocket endpoint or usage guidance. Done means identifying whether the endpoint is unavailable or the connection instructions are incomplete, then documenting the confirmed resolution or next steps.

Written by the indexing model from the issue text.