docs: improve text decoration

Author: kenjis

user_guide_src/source/general/environments.rst

@@ -16,9 +16,9 @@ tools loaded that you don't in production environments, etc.
 The ENVIRONMENT Constant
 ========================
 
-By default, CodeIgniter comes with the environment constant set to use
+By default, CodeIgniter comes with the ``ENVIRONMENT`` constant set to use
 the value provided in ``$_SERVER['CI_ENVIRONMENT']``, otherwise defaulting to
-'production'. This can be set in several ways depending on your server setup.
+``production``. This can be set in several ways depending on your server setup.
 
 .. note:: The environment ``testing`` is the special one for PHPUnit testing.
     It has special conditions built into the framework at various places to assist with that.