nir/spirv: Remove unnecessary comment.
It should have been removed after 00c47e11. Cc: Jason Ekstrand <jason@jlekstrand.net> Cc: Connor Abbott <cwabbott0@gmail.com> Signed-off-by:Andres Gomez <agomez@igalia.com> Reviewed-by:
Jason Ekstrand <jason@jlekstrand.net>