Remove mbstring.func_overload

Deprecated in PHP 7.2 as part of
https://wiki.php.net/rfc/deprecations_php_7_2.

php.ini-production

@@ -1672,17 +1672,6 @@ zend.assertions = -1
 ; http://php.net/mbstring.substitute-character
 ;mbstring.substitute_character = none
 
-; overload(replace) single byte functions by mbstring functions.
-; mail(), ereg(), etc are overloaded by mb_send_mail(), mb_ereg(),
-; etc. Possible values are 0,1,2,4 or combination of them.
-; For example, 7 for overload everything.
-; 0: No overload
-; 1: Overload mail() function
-; 2: Overload str*() functions
-; 4: Overload ereg*() functions
-; http://php.net/mbstring.func-overload
-;mbstring.func_overload = 0
-
 ; enable strict encoding detection.
 ; Default: Off
 ;mbstring.strict_detection = On