weibo: fix bad artist name suggestions in new artist form.

Fix the new artist form suggesting invalid Chinese tag names for Weibo
artists. Suggest `weibo_123456` instead as a placeholder.

app/logical/source/extractor/weibo.rb

@@ -47,14 +47,14 @@ module Source
         end
       end
 
-      def profile_urls
-        [parsed_url.profile_url, parsed_referer&.profile_url].compact.uniq
-      end
-
       def profile_url
         "https://www.weibo.com/u/#{artist_id}" if artist_id.present?
       end
 
+      def tag_name
+        "weibo_#{artist_id}" if artist_id.present?
+      end
+
       def artist_name
         api_response&.dig("user", "screen_name")
       end