* operating-systemd.html: add a warning for Linux/CPU vulns
* operating-systems: expand the Linux instructions for MDS mitigation
* operating-systems: s/multithreading/hyperthreading/
* operating-systems: address feedback, fix typo
* operating-systems: remove update-grub, close li tags
* operating-systems: @nitrohorse's first feedback
Doing this in a separate commit in case I misunderstood, so I can revert
* operating-systems: address feedback
* operating-systems: dd a duplicate paragraph
* operating-systems: add missing "grub" word
* operating-systems: fix the last step of nosmt
* operating-systems: mention macOS link
* operating-systems: address feedback
* operating-systems: add a dot
* operating-systems: fix link