Remove mention to Flex

Author: pyrech

deployment/proxies.rst

@@ -90,13 +90,12 @@ and what headers your reverse proxy uses to send information:
 
 .. tip::
 
-    In applications using :ref:`Symfony Flex <symfony-flex>` you can set the
-    ``TRUSTED_PROXIES`` env var:
+    You can set a ``TRUSTED_PROXIES`` env var to configure proxies on a per-environment basis:
 
     .. code-block:: bash
 
         # .env
-        TRUSTED_PROXIES=127.0.0.1
+        TRUSTED_PROXIES=127.0.0.1,10.0.0.0/8
 
     .. code-block:: yaml