FIX: Remove broken narrative-bot search context logic (#26319)

In the past we had logic to automatically set the search context to the current topic during the tutorial. This hasn't worked for a long time, and clearly people have still been able to complete the tutorial. In fact, it's probably better for us to teach people how to use the search un-assisted anyway.

This commit removes the dead logic, and makes a slight tweak to the copy in the unlikely event of confusion.

plugins/discourse-narrative-bot/lib/discourse_narrative_bot/new_user_narrative.rb

@@ -173,12 +173,6 @@ module DiscourseNarrativeBot
       topic = @post.topic
       post = topic.first_post
 
-      MessageBus.publish(
-        "/new_user_narrative/tutorial_search/#{@user.id}",
-        {},
-        user_ids: [@user.id],
-      )
-
       raw = <<~MD
       #{post.raw}