Add Homebrew and ASDF security update instructions
What does this MR do?
Adds instructions for updating Homebrew and ASDF packages for security updates.
Why was this MR needed?
The process was not documented.
What's the best way to test this MR?
Use the playbook development setup described here: https://gitlab.com/gitlab-org/ci-cd/shared-runners/images/macstadium/orka/-/blob/7fbc542e813984611577c74fbd19dea7539e491f/README.md#develop-on-the-ansible-playbooks