fix websocket reload loop
Created by: sqs
For some reason, Webpack started showing "Invalid frame header" JS console errors on all pages, and on Monaco editor pages it would get into a reload loop. This only occurred on dev servers, not in prod. I don't know why this happened; even after reverting the recent changes related to Webpack, it was still occurring.
Removing WebSocket proxying in webpack-dev-server fixes the issue. We don't need it to proxy WebSockets anymore because the main Sourcegraph app no longer exposes any WebSocket endpoints.