bp_blogs_delete_new_blog_activity_for_site( int $blog_id,  $user_id )

function bp_blogs_delete_new_blog_activity_for_site( $blog_id, $user_id = 0 ) {
	$args = array(
		'item_id'   => $blog_id,
		'component' => buddypress()->blogs->id,
		'type'      => 'new_blog'
	);

	/**
	 * In the case a user is removed, make sure he is the author of the 'new_blog' activity
	 * when trying to delete it.
	 */
	if ( ! empty( $user_id ) ) {
		$args['user_id'] = $user_id;
	}

	bp_blogs_delete_activity( $args );
}