Delete/replace h2 tag widget title

Hello,

I’ve got a nasty empty <h2> in my homepage code. I want to delete it, or at worst, replace it by a <p> or <span>. It seems that Mailjet is the culprit:

    <!--Widget title-->
    <div id="mailjet-widget-title-wrap">
            <h2 class="widgettitle"></h2>    </div>
    <!--End Widget title-->

For now, I couldn’t find where to modify this. Could you tell?

I want to do this for SEO reasons.

Thanks!