nir: remove ubo_r600 instrinsic since ubo_vec4 is used now

As suggested by Eric.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
eviewed-by: Eric Anholt <eric@anholt.net>

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6743>
1 file changed