This function uses ff_sws_pixel_type_size to switch on the
size of the provided type. However, ff_sws_pixel_type_size returns
a size in bytes (from sizeof()), not a size in bits. Therefore,
this would previously never return the right thing but always
hit the av_unreachable() below.
As the function is entirely unused, just remove it.
This fixes compilation with MSVC 2026 18.0 when targeting ARM64,
which previously hit an internal compiler error [1].
[1] https://developercommunity.visualstudio.com/t/Internal-Compiler-Error-targeting-ARM64-/10962922
3cc1dc3358