Update deployment.rst

Author: proArtex

deployment.rst

@@ -156,7 +156,7 @@ as you normally do:
 .. caution::
 
     If you get a "class not found" error during this step, you may need to
-    run ``export SYMFONY_ENV=prod`` before running this command so that
+    run ``export APP_ENV=prod`` before running this command so that
     the ``post-install-cmd`` scripts run in the ``prod`` environment.
 
 D) Clear your Symfony Cache