WordPress 5: including larger thumbnail image sizes in srcset than I have set

Good question as I know that this can be a pain in the butthole. Please see this page; https://developer.wordpress.org/reference/functions/get_the_post_thumbnail_url/.

From the docs:

get_the_post_thumbnail_url($id, 'image-size')

So in your case:

$img = get_the_post_thumbnail_url($post, 'article-lede');
echo "<img src="https://wordpress.stackexchange.com/questions/353305/{$img}" class="featured-image img-fluid" />";