Didn't entirely work for me. I still had the little popup when I selected text, even after restarting. However, it did go away and stay away when I selected "hide chatbot..." at the bottom of the popup.
>>strong+(OP)
about:config, type ".ml." in the search (no quote marks), set everything to false / zero / blank.
I don't want anything even vaguely related to spicy autocomplete on any of my machines, and I go to great lengths to kill anything that even resembles it with fire.