webpack: Remove unused hexoid alias.

koa-body was switched to @koa/bodyparser during development of #29198,
so this was never used.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

web/webpack.config.ts

@@ -278,12 +278,6 @@ const config = (
         output: {
             path: path.resolve(__dirname, "../static/webpack-bundles"),
         },
-        resolve: {
-            alias: {
-                // koa-body uses formidable 2.x, which suffers from https://github.com/node-formidable/formidable/issues/337
-                hexoid: "hexoid/dist/index.js",
-            },
-        },
     };
 
     return [frontendConfig, serverConfig];