chore(snowflakes): don't remove file lock directory during tests

Signed-off-by: Benjamin Gaussorgues <benjamin.gaussorgues@nextcloud.com>

tests/lib/Snowflake/FileSequenceTest.php

@@ -30,6 +30,5 @@ class FileSequenceTest extends ISequenceBase {
 		foreach (glob($lockDirectory . '/*') as $file) {
 			unlink($file);
 		}
-		rmdir($lockDirectory);
 	}
 }