docs: change text decoration

Author: kenjis

user_guide_src/source/general/environments.rst

@@ -97,7 +97,7 @@ is affected.
 Error Reporting
 ---------------
 
-Setting the ENVIRONMENT constant to a value of 'development' will cause
+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
 output. Disabling error reporting in production is a