Do not call ReflectionProperty::setAccessible() when not needed

Author: kubawerlos

tests/AbstractProcessTest.php

@@ -70,7 +70,9 @@ public function testStartWithoutLoopAssignsLoopAutomatically()
         $process->start();
 
         $ref = new \ReflectionProperty($process->stdin, 'loop');
-        $ref->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $loop = $ref->getValue($process->stdin);
 
         $this->assertInstanceOf('React\EventLoop\LoopInterface', $loop);