docs: change text decoration

Author: kenjis

user_guide_src/source/general/environments.rst

@@ -99,7 +99,7 @@ Error Reporting
 
 Setting the ENVIRONMENT constant to a value of ``development`` will cause
 all PHP errors to be rendered to the browser when they occur.
-Conversely, setting the constant to 'production' will disable all error
+Conversely, setting the constant to ``production`` will disable all error
 output. Disabling error reporting in production is a
 :doc:`good security practice </concepts/security>`.