Remove no longer needed index.web.dev.html

Summary: This is a duplicate, is not needed, causes confusion.

Reviewed By: aigoncharov

Differential Revision: D51307091

fbshipit-source-id: 4d55d727ea5f20100ecd15ad6e23aa0c01722524

desktop/flipper-server-core/src/server/startServer.tsx

@@ -185,7 +185,6 @@ async function startHTTPServer(
   };
   app.get('/', serveRoot);
   app.get('/index.web.html', serveRoot);
-  app.get('/index.web.dev.html', serveRoot);
 
   app.get('/ready', (_req, res) => {
     tracker.track('server-endpoint-hit', {name: 'ready'});