It's unlikely, but I never set up or used an old blockchain.info wallet so I'm not 100% sure though. This would be very insecure, but blockchain.com aren't exactly known for their good security of technical competence. They did used to email users their wallet.aes.json file to save as a back up, so its not outside the realm of possibilities that they also emailed out your password recovery phrase. More likely though is that you would simply have been shown it when setting up your wallet for the first time and told to write it down or save it somewhere safe. It would be a list of 16-20 seemingly random and unconnected words. If you don't remember such a thing, then it's probably not worth wasting your time on, and you would be better off just trying to remember as much as you can about your password for your brute force attempt.