docs(dav): remove outdated comment

The method was added actually to PHP API in 28 and the mentioned check
is not in place anymore.

Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>

apps/dav/lib/Connector/Sabre/FilesReportPlugin.php

@@ -334,8 +334,6 @@ class FilesReportPlugin extends ServerPlugin {
 
 		$nodes = [];
 
-		// type check to ensure searchBySystemTag is available, it is not
-		// exposed in API yet
 		if (!empty($systemTagIds)) {
 			$tags = $this->tagManager->getTagsByIds($systemTagIds, $this->userSession->getUser());