suppress resizing of feature image on single posts

Hello Raam!
Many thanks for this great theme! I have a question regarding featured images which I haven’t seen answered yet, neither here nor on GitHub. If I missed it and this is a duplicate issue, I’m very sorry.

I want single posts (or all posts) to display the featured image in its uploaded size (for example 300×300). But Independent Publisher is resizing featured images on posts to 700×700 (or 700 in height). I had no success in trying to change or suppress this.

In the child theme, I edited content-single-php to change

<?php if ( has_post_thumbnail() && !independent_publisher_has_full_width_featured_image() ) : ?>
		<?php the_post_thumbnail( 'independent_publisher_post_thumbnail', array( 'itemprop' => 'image' ) ); ?>

to simply

<?php if ( has_post_thumbnail() ) { the_post_thumbnail(); } ?>

but I can see no effect. Is the theme generally styling the featured image? I’m stuck with this, any help is appreciated. My alternative would be to not display the featured image and manually add it inside the post (not ideal).