Apparently, with the move to One D&D, WotC have decided to remove half-elves and half-orcs as 'species' options in their own right - players will be advised to choose whichever of human and elf/orc makes for the closer match for their character, and go with that. (This does have the advantage that it makes half-dwarves, half-halflings, elf-dwarves, or whatever trivially easy to handle.)
On the one hand, I'm not keen on this approach - for all that it's probably driven by their drive to remove problematic material, it feels like they're doing it by erasure of mixed-race folk, which seems rather counter-productive. Plus, of course, every edition of the game that has removed half-orcs has failed abysmally. (And I would prefer not to have orcs as a PC race. But that ship has long since sailed.)
On the other hand, I'm inclined to think that a better approach to mixed species in general would be to introduce "elf heritage" traits alongside each species description, allowing people to mix and match species as they go (and even allow those to be selected later to handle "discovered heritages" during play).
But, actually, I'm now coming to the view that the thing to do with species is to remove it from the mechanical expression of a character entirely. Instead, transfer all the various racial traits (darkvision and the like) into feats/advantages/traits/whatever, and then allow the player to choose from the wider list as they want. The character can then be described as belonging to any of the species (or a mix of any of the species) that exist in the setting.
(Ultimately, I don't think it matters if Gimli has darkvision because of his dwarven heritage, Geralt has darkvision because of his mutations, or Arya has darkvision because of her mystical training - it's the same trait, and all justifications work. And, likewise, one could easily argue that a dwarf who has lived his whole life on the surface may lack darkvision entirely, as it has atrophied with time.)