I would argue that, unless prohibited by name, a rifle capable of firing only one shot - even though it may happen to look like a popular style of semi-auto rifle - is, by definition, a single shot rifle.
If it is legal to use a magazine spacer to make a five-shot capable shotgun into a legal three-shot duck gun, why would an AR that's been converted to shoot single-shot-only be any different?
Of course, I will also not be posting your bail in the event that the local enforcement body disagrees with my assessment of the situation. So, it would probably be best to contact the local governing body and pose the question to them - preferably in writing.
On another note, I would think that there are much better platforms for a deer rifle than a single-shot AR. I would imagine that a standard break-action single-shot rifle would be quite a bit faster if there ever arises a need to take a follow up shot. And, I would think that even the worst, clunkiest, grittiest bolt action would still be head and shoulders above any single-shot AR in this case.
That's my two cents worth of advice. And it's probably worth just about what you paid for it.