Merge pull request #5450 from totoprayogo1916/update/userguide

update docs about `esc()`

Author: kenjis

system/Common.php

@@ -380,7 +380,7 @@ function env(string $key, $default = null)
      * If $data is an array, then it loops over it, escaping each
      * 'value' of the key/value pairs.
      *
-     * Valid context values: html, js, css, url, attr, raw, null
+     * Valid context values: html, js, css, url, attr, raw
      *
      * @param array|string $data
      * @param string       $encoding

user_guide_src/source/general/common_functions.rst

@@ -81,7 +81,7 @@ Service Accessors
     If $data is a string, then it simply escapes and returns it.
     If $data is an array, then it loops over it, escaping each 'value' of the key/value pairs.
 
-    Valid context values: html, js, css, url, attr, raw, null
+    Valid context values: html, js, css, url, attr, raw
 
 .. php:function:: helper($filename)