spirv: Remove outdated SPIR-V decoration warnings

spirv: Remove outdated SPIR-V decoration warnings

spirv_to_nir warns if it encounters XFB decorations and errors if
it encounters a Stream decoration with value other than 0, despite
the fact that these decorations are in fact handled correctly.

Fixes dEQP-VK.transform_feedback.simple.query_1_*
Fixes: cd4a14be06 "spirv: Handle XFB variable decorations"
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3910>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3910>