eslint: Fix unicorn/prefer-spread.

This was initially disabled for IE/Babel-related reasons that no
longer apply.

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

web/src/bot_data.js

@@ -23,7 +23,7 @@ const services = new Map();
 const services_fields = ["base_url", "interface", "config_data", "service_name", "token"];
 
 export function all_user_ids() {
-    return Array.from(bots.keys());
+    return [...bots.keys()];
 }
 
 export function add(bot) {