vc4: Stop advertising support for VS color clamping.

This is special GL behavior that the frontend is now able to handle for
us.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8601>

src/gallium/drivers/vc4/vc4_program.c

@@ -2298,9 +2298,6 @@ vc4_shader_ntq(struct vc4_context *vc4, enum qstage stage,
 
         NIR_PASS_V(c->s, nir_lower_tex, &tex_options);
 
-        if (c->vs_key && c->vs_key->clamp_color)
-                NIR_PASS_V(c->s, nir_lower_clamp_color_outputs);
-
         if (c->key->ucp_enables) {
                 if (stage == QSTAGE_FRAG) {
                         NIR_PASS_V(c->s, nir_lower_clip_fs,
@@ -2785,7 +2782,6 @@ vc4_update_compiled_vs(struct vc4_context *vc4, uint8_t prim_mode)
         vc4_setup_shared_key(vc4, &key->base, &vc4->verttex);
         key->base.shader_state = vc4->prog.bind_vs;
         key->fs_inputs = vc4->prog.fs->fs_inputs;
-        key->clamp_color = vc4->rasterizer->base.clamp_vertex_color;
 
         for (int i = 0; i < ARRAY_SIZE(key->attr_formats); i++)
                 key->attr_formats[i] = vc4->vtx->pipe[i].src_format;