The websocket connection to Discord dropped mid-stream and the bot is auto-restarting.
A network interruption, the machine sleeping, or Discord closing an idle connection. The broken pipe is the socket layer reporting the dropped stream.
The bot auto-restarts from this, so no action is needed in most cases. If it loops, stabilize the host network or disable sleep/hibernate on the machine. On a VPS, check for memory pressure killing the process.