Fix flaky test by freezing time before write operation (#57903)

This prevents timing race conditions where time can advance between
when the session is written (which records a timestamp) and when
the expiration check occurs, causing intermittent test failures.

Author: sumaiazaman

tests/Session/ArraySessionHandlerTest.php

@@ -48,6 +48,7 @@ public function test_it_reads_data_from_an_almost_expired_session()
     {
         $handler = new ArraySessionHandler(10);
 
+        Carbon::setTestNow(Carbon::now());
         $handler->write('foo', 'bar');
 
         Carbon::setTestNow(Carbon::now()->addMinutes(10));