Update thread-request box to be less leading and more helpful

// This program demonstrates the current behavior of the RFC thread‑request box.
// Since the change only updates UI text, we cannot programmatically show it.
// Instead, we print the new instruction text to illustrate what a user would see.

fn main() {
    // New instruction shown on the RFC review page
    println!("Since RFCs involve many conversations at once that can be difficult to follow, please use review comment threads on the text changes instead of direct comments on the RFC.");
    println!("If you don't have a particular section of the RFC to comment on, you can click on the \"Comment on this file\" button on the top-right corner of the diff, to the right of the \"Viewed\" checkbox. This will create a separate thread even if others have commented on the file too.");
}