This line of code is responsible for featured images in single posts view and blog. To remove images from blog page you should edit this line from
content.php file and for single post view you should remove this line from
<?php the_post_thumbnail( 'sparkling-featured', array( 'class' => 'single-featured' )); ?>
These changes can be done via Child Theme by copy-pasting
content.php to Child Theme and then you can edit those newly created files on Child Theme folder.
Alternatively you can simply add this code to Theme Options - Other - Custom CSS and featured images will be hidden but still loaded. So this might slightly affect website performance as it would appear that images are there but not visible for user.
Let me know if this helps.