ext/standard: fix wrong array_filter() default value

Follow-up to GH-21100, that mistakenly set the default value of
the `array_filter()` as `ARRAY_FILTER_USE_KEY`, when it should
be `ARRAY_FILTER_USE_VALUE`, which is the newly defined constant.

Author: Ayesh

ext/standard/basic_functions.stub.php

@@ -1879,7 +1879,7 @@ function array_product(array $array): int|float {}
 
 function array_reduce(array $array, callable $callback, mixed $initial = null): mixed {}
 
-function array_filter(array $array, ?callable $callback = null, int $mode = ARRAY_FILTER_USE_KEY): array {}
+function array_filter(array $array, ?callable $callback = null, int $mode = ARRAY_FILTER_USE_VALUE): array {}
 
 function array_find(array $array, callable $callback): mixed {}