message_scroll: Remove misleading comment.

The hacky code referenced in this comment was removed in
d59ccd4c0f.

static/js/message_scroll.js

@@ -80,11 +80,8 @@ export function hide_end_of_results_notice() {
 
 export function show_end_of_results_notice() {
     $(".all-messages-search-caution").show();
+
     // Set the link to point to this search with streams:public added.
-    // It's a bit hacky to use the href, but
-    // !filter.includes_full_stream_history() implies streams:public
-    // wasn't already present.
-    // Computes the URL of the current narrow if streams:public were added.
     const operators = narrow_state.filter().operators();
     const update_hash = hash_util.search_public_streams_notice_url(operators);
     $(".all-messages-search-caution a.search-shared-history").attr("href", update_hash);