tools: fix formatting of warning message in update-authors.js

The email already has `<` and `>` surrounding it so adding it results in
a misformatted message.

PR-URL: https://github.com/nodejs/node/pull/40600


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Voltrex <mohammadkeyvanzade94@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>