fix: replace rand() with random_int() and intdiv() in getTimeoutMicroseconds()

rand() (mt_rand) offers weaker uniformity than random_int(), and passing
  $timeout / 10 (float) to rand()'s int parameters triggers a deprecation
  warning in PHP 8.1+. Switch to random_int() for better distribution and
  use intdiv() to ensure the upper bound is always an integer.

Author: deminy

src/ExponentialBackoff.php

@@ -189,7 +189,7 @@ public static function getTimeoutMicroseconds(int $iteration, int $initialTimeou
         $timeout = $initialTimeout * (1 << --$iteration);
 
         // We throw in some randomness here to try to prevent connections from colliding
-        return $timeout + rand(0, $timeout / 10);
+        return $timeout + random_int(0, intdiv($timeout, 10));
     }
 
     protected function increaseCurrentAttempts(): self