The option to “discard” suggested contacts in your chat list is rolling out to users. We will be making further changes to make suggested contacts more relevant for new users in the future as well, so marking as partially completed. Thanks for your patience with this one.
~Alex & the Teams teamJames commented
Both people showing in my suggested contacts are no longer with my organization, in fact, one of them left 10 months ago. The other only left 6 months ago. It's really silly that I'm seeing them appear there, it's a dumb oversight by Microsoft to allow this to persist.