Introduce a fix to stop caching the html for the announcement post

[globalistas]

This to address the issue where anons see an announcement post as upvoted by them. Logged in users see it upvoted by themselves too, even though they have not voted.

Not sure if this is related to me having re-created the post before this started happening.

[globalistas]

I have just noticed the same issue on sticky posts, so those might need looking into as well.