Remove the referrer from Webserver to Scarf (apache#42901)

This will make sure we don't receive any information about the Webserver URL sending the info like the number of plugins and such.

airflow/www/templates/airflow/dags.html

@@ -489,6 +489,6 @@ <h2>{{ page_title }}</h2>
     }
   </script>
   {% if scarf_url %}
-  <img referrerpolicy="no-referrer-when-downgrade" src="{{ scarf_url }}" width="0" height="0" alt="" style="display:none;" />
+  <img referrerpolicy="no-referrer" src="{{ scarf_url }}" width="0" height="0" alt="" style="display:none;" />
   {% endif %}
 {% endblock %}

docs/apache-airflow/faq.rst

@@ -548,4 +548,3 @@ The telemetry data collected is limited to the following:
 - Number of DAGs
 - Number of Airflow plugins
 - Number of timetables, Flask blueprints, Flask AppBuilder views, and Flask Appbuilder menu items from Airflow plugins
-- and information from tracking pixels like URL / IP-address as documented in the `Scarf Privacy Policy <https://about.scarf.sh/privacy-policy>`__.