Update NEWS/UPGRADING for $http_response_header deprecation

Author: Girgias

NEWS

@@ -30,6 +30,8 @@ PHP                                                                        NEWS
   . Prohibit pipe & arrow function combination that leads to confusing parse
     trees. (ilutov)
   . The disable_classes INI directive has been removed. (Girgias)
+  . The locally predefined variable $http_response_header is deprecated.
+    (Girgias)
 
 - Filter:
   . Added support for configuring the URI parser for FILTER_VALIDATE_URL

UPGRADING

@@ -464,6 +464,9 @@ PHP 8.5 UPGRADE NOTES
   . Passing integers outside the interval [0, 255] to chr() is now deprecated.
     This is because a byte can only hold a value within this interval.
     RFC: https://wiki.php.net/rfc/deprecations_php_8_5#deprecate_passing_integers_outside_the_interval_0_255_to_chr
+  . Relying locally predefined variable $http_response_header is deprecated.
+    Instead one should call the http_get_last_response_headers() function.
+    RFC: https://wiki.php.net/rfc/deprecations_php_8_5#deprecate_the_http_response_header_predefined_variable
 
 - XML:
   . The xml_parser_free() function has been deprecated, as XMLParser objects