Probably you'll be just fine, although it's technically outside the spec'd range.
Per the Shimano 2019-2020 Products compatibility Information document (warning: PDF link), the RD-R8000 rear derailleur is compatible with all of the following cassettes:
As far as I know, that covers all of Shimano's 11-speed road cassettes, and I'm assuming Shimano doesn't produce an 11-23 MTB cassette.
The RD-R8000 is spec'd as
(25T≤CS Low gear≤30T)
(the GS is similary spec'd with a 28T minimum)
so a 23-tooth sprocket would be slightly too small per Shimano's specs.
But it should work for you as Shimano's spec's are notoriously tight - and I already do have an 11-23 on a bike with an RD-8000-SS and it works fine with an 11-23. (I didn't even know it wasn't "in spec"...)
The page the info was extracted from: