Hello,
You'll notice these files are permissioned with root.root and 600, therefore, only root can read them. Since the root user can log into to MySQL, or anything else for that matter, without needing any credentials, this is not a security risk.
That said, you are free to remove the /tmp/*kalt*.ans from the disk post installation, they are only created for your convenience so that, when upgrading or reconfiguring, you won't have to reinput all the answers manually, they are not needed for the system's day to day operation.
Thanks,