How to remove the nag

Several people have mentioned wanting to remove the “nag” button.
You may be able to do this by adding the following to your theme’s functions.php file, adding in any custom post types you may be using (in this example: cd_listing, articles). That being said, the paid version is cheap enough!

//removes “preview & view” options from the new post and post edit admin screens
//Enter any post type you would like to remove the “view and preview” buttons from “custom post type, post, page
//http://wpsnipp.com/index.php/functions-php/hide-post-view-and-post-preview-admin-buttons/
function posttype_admin_css() {
	global $post_type;
	$post_types = array( 'post',
					'page',
					'misc',
					'articles',
					'cd_listing'
				  );
	if ( in_array($post_type, $post_types) )
	echo '<style type="text/css">.button.imgevr-get-premium, #post-preview, #view-post-btn{display: none;}</style>';
}
add_action( 'admin_head-post-new.php', 'posttype_admin_css' );
add_action( 'admin_head-post.php', 'posttype_admin_css' );

https://wordpress.org/plugins/image-elevator/