Modify "_blank" to "_self" for Privacy link in form

I am using the Newsletter plugin on a site. Now, in the form one has a checkbox and a link to read the Privacy policy. This links sends the user to a new page. I want to load this URL in the same page. I've tried to alter this but I haven't succeed.

In my WP page I've just included this:
[newsletter_form]
That creates the form with the fields I indicated in the configuration.

According to the plugin, this is (a part of) the code that is generated automatically:
<div class="tnp-field tnp-field-privacy"><label><input type="checkbox" name="ny" required class="tnp-privacy"> Ich akzeptiere die Datenschutzbestimmungen</label></div>

I can see the target parameter is set to "_blank". I want to switch it to "_self". How can I modify that?

This is the web I am working on:
https://www.mobilestheaterspunk.de/site/kontakt

Any help would be appreciated. Thanks in advance.