Using the non-temporal AVX engine for unknown CPU types looks like a mistake to
me, and the default built into the switch case is to use the fallback engine. I
don't think this is causing issues now, but it might once we add ARM support.

PiperOrigin-RevId: 561097994
Change-Id: I7f0edd447017c09acd49e4ea11476e32740d630a