use debug log level, when node not found in ViewOnlyPlugin

apps/dav/lib/DAV/ViewOnlyPlugin.php

@@ -109,7 +109,7 @@ public function checkViewOnly(
 				throw new Forbidden('Access to this resource has been denied because it is in view-only mode.');
 			}
 		} catch (NotFound $e) {
-			$this->logger->warning($e->getMessage());
+			$this->logger->debug($e->getMessage());
 		}
 
 		return true;