wordpress-theme 2017: featured image behaviour: where to set the height of the featured image?

Navigate to theme folder of “twentyseventeen” and open the functions.php file.
Now, Goto line no. “54” and you will see below code.

add_image_size( 'twentyseventeen-featured-image', 2000, 1200, true );

You can change the dimensions there.

Thanks,