backend: update deno version for websocket panic fix
We previously ran into a fatal race condition in deno's WebSocket stack. See https://github.com/denoland/deno/issues/14240#issuecomment-1270647068 for details.
This issue was fixed in the v1.36.1 release: https://github.com/denoland/deno/issues/14240#issuecomment-1675729271