eslint: Fix unicorn/better-regex.

https://github.com/sindresorhus/eslint-plugin-unicorn/blob/master/docs/rules/better-regex.md

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

static/js/settings_bots.js

@@ -68,7 +68,7 @@ function is_local_part(value, element) {
     // Adapted from Django's EmailValidator
     return (
         this.optional(element) ||
-        /^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*$/i.test(value)
+        /^[\w!#$%&'*+/=?^`{|}~-]+(\.[\w!#$%&'*+/=?^`{|}~-]+)*$/i.test(value)
     );
 }