i386/cpu: Drop incorrect comment for CPUID 0x1D

i386/cpu: Drop incorrect comment for CPUID 0x1D

The information in CPUID 0x1D.0x1 is for tile palette 1, and is not
SPR-specific.

This is to say, these "hardcoded" values won't change in future. If
the palette needs to be extended, a new tile palette (maybe in a new
subleaf) will be introduced instead of changing current information of
tile palette 1.

Furthermore, the previous attempt [*] to make the 0x1D.0x1 fields
user-configurable is incorrect and unnecessary.

Therefore, drop the incorrect and misleading comment.

[*]: https://lore.kernel.org/qemu-devel/20230106083826.5384-2-lei4.wang@intel.com/

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20251118080837.837505-2-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>