[AIRFLOW-XXX] Improve linking in docs (#6244)

docs/concepts.rst

@@ -826,6 +826,8 @@ For example a ``html_content_template`` file could look like this:
   Log file: {{ti.log_filepath}}<br>
   Mark success: <a href="{{ti.mark_success_url}}">Link</a><br>
 
+.. _concepts/trigger_rule:
+
 Trigger Rules
 =============
 

docs/faq.rst

@@ -84,14 +84,12 @@ sure you fully understand how it proceeds.
 How do I trigger tasks based on another task's failure?
 -------------------------------------------------------
 
-Check out the ``Trigger Rule`` section in the Concepts section of the
-documentation.
+Check out the :ref:`concepts/trigger_rule`.
 
 Why are connection passwords still not encrypted in the metadata db after I installed airflow[crypto]?
 ------------------------------------------------------------------------------------------------------
 
-Check out the ``Securing Connections`` section in the How-to Guides section of the
-documentation.
+Check out the :doc:`howto/secure-connections`.
 
 What's the deal with ``start_date``?
 ------------------------------------