docs/(demo): update demo system prerequisites
Updates README.md to remove OpenSSL/LibreSSL system prerequisite as it is no longer needed
## System Requirements
- Go version 1.14 or higher
-- OpenSSL/LibreSSL 2.8.3 or higher
- Kubectl version 1.16 or higher
- Docker CLI
- on a Debian based GNU/Linux system: `sudo apt-get install docker`
