Optimization of CSS Delivery ?

https://developers.google.com/speed/pagespeed lists the CSS delivery as CSS in above-the-fold content that can reduce the speed of the website, in my case, it points at:

https://www.comicsenglish.com/wp-content/plugins/wysija-newsletters/css/validationEngine.jquery.css?ver=2.5.9.4

Anything can be done to improve that?

Thanks for your great plugin!

https://www.ads-software.com/plugins/wysija-newsletters/