This is metadata for oneboxing, so that when someone posts a link to your website on Twitter it can show you what the link contains.
No more information is exposed than what is already public.
This is the value of your facebook_app_id site setting so the Discourse client can use it if it’s configured for login. Don’t set it and it won’t have a value.
Removing the presence of those arbitrary strings in the HTML you serve would not serve any practical purpose; any fears based on the presence of them are unfounded.
If it would make your visitors more… comfortable… you could set up a web filter to blindly search and replace the words twitter and facebook in your responses? That’ll probably break something (e.g. settings editing) and they would no longer be able to talk about REDACTED or REDACTED, but it would do.
I don’t see anything actionable here that serves a meaningful purpose.
Do you have a specific goal other than “don’t talk about X”?