test: remove ReflectionProperty::setAccessible() deprecated since PHP 8.5

setAccessible() has been a no-op since PHP 8.1 and is deprecated since PHP 8.5.

Signed-off-by: Anna Larch <anna@nextcloud.com>
AI-Assisted-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: miaulalala

tests/lib/Files/Mount/RootMountProviderTest.php

@@ -85,7 +85,6 @@ public function testObjectStore(): void {
 
 		$class = new \ReflectionClass($storage);
 		$prop = $class->getProperty('objectStore');
-		$prop->setAccessible(true);
 		/** @var S3 $objectStore */
 		$objectStore = $prop->getValue($storage);
 		$this->assertEquals('nextcloud', $objectStore->getBucket());