Since the WordPress is calling the `make_clickable` function in terms of the `comment_text` filter, Instagram oEmbedes containing a plaintext link are not being properly initialised as Instagram's JS expects only a single `a` element inside the `blockquote`.

This commit is programmatically removing the script element using DomDocument and is appending a custom one, which 1) load the original script only if it has not been loaded before 2) initialise the Instagram oEmbed manually (as a side effect this fixes the issue with Instagram oEmbeds not properly working when clicking the preview button multiple times).

This commit removes the DOM Document parsing of the oEmbed response in favour of taking advantage of `oembed_fetch_url` filter for requesting the oEmbed without the script