Review `om health` "Fix" messages

[srid]

For eg., does it make sense to link to nixos.wiki on "Enable flakes"? Or does it make more sense to suggest the user to use the DetSys installer? @shivaraj-bh noted somewhere that we may want to be smart about these Fix messages, for eg., by recommending nixone but only for Juspay'ers.

[brainrake]

Related: Don't use or recommend trusted-users. It gives you root without password.

#409