Open System Settings / Keyboard / Keyboard Shortcuts / Services / Searching, then either double-click on the shortcut for "Search with FoxTrot" (press the delete key to remove the shortcut), or uncheck "Search with FoxTrot" to completely remove this command from the Services menu
Oh, thanks a bunch! By the way, for future reference, are these shortcuts stored in a Foxtrot-searchable form anywhere so I could search for "⇧⌘X" and find it? Or at least search for "Foxtrot" and also find this? Maybe I'm just missing the files in the indexing