median() div swapped for intdiv() (#57148)

Finding the middle of a list of values using the float div operator (/) is wrong, and goes wrong at some higher values where the int/2 is not representable as a float to single digit precision. 

That's why intdiv() exists.

Author: artumi-richard

src/Illuminate/Collections/Collection.php

@@ -95,7 +95,7 @@ public function median($key = null)
             return;
         }
 
-        $middle = (int) ($count / 2);
+        $middle = intdiv($count, 2);
 
         if ($count % 2) {
             return $values->get($middle);