refactor: remove description and rules mock posts

Removed all fake posts for subplebbit description and rules, including dedicated routes, components, and all related logic across the codebase. Board admins can now pin regular posts if they want to provide a description.

src/hooks/use-replies.ts

@@ -53,11 +53,6 @@ const useReplies = (comment: Comment) => {
     });
   }, [flattenedReplies, accountRepliesNotYetPublished]);
 
-  // if the comment is a fake comment for description or rules, return an empty array
-  if (comment?.isDescription || comment?.isRules) {
-    return [];
-  }
-
   return repliesAndNotYetPublishedReplies;
 };