Update redis.config.php

add dbindex for redis as comment. referenced from a6f2a3c commit

Signed-off-by: Arjun Santhosh <139119101+Hujgo@users.noreply.github.com>

.config/redis.config.php

@@ -6,6 +6,7 @@ if (getenv('REDIS_HOST')) {
     'redis' => array(
       'host' => getenv('REDIS_HOST'),
       'password' => getenv('REDIS_HOST_PASSWORD_FILE') && file_exists(getenv('REDIS_HOST_PASSWORD_FILE')) ? trim(file_get_contents(getenv('REDIS_HOST_PASSWORD_FILE'))) : (string) getenv('REDIS_HOST_PASSWORD'),
+      'dbindex' => (int) getenv('REDIS_DB_INDEX'),
     ),
   );