Keep config.php group-writable

Signed-off-by: Jérôme Lafréchoux <jerome@jolimont.fr>

Author: lafrech

lib/private/Config.php

@@ -283,7 +283,7 @@ private function writeData(): void {
 		$filePointer = fopen($this->configFilePath, 'r+');
 
 		// Prevent others not to read the config
-		chmod($this->configFilePath, 0640);
+		chmod($this->configFilePath, 0660);
 
 		// File does not exist, this can happen when doing a fresh install
 		if (!is_resource($filePointer)) {