tgsi: remove culldist semantic from docs

The semantic was removed in e6d9389366.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/gallium/docs/source/tgsi.rst

@@ -3205,24 +3205,6 @@ tessellation evaluation shaders, respectively. Only the value written in the
 last vertex processing stage is used.
 
 
-TGSI_SEMANTIC_CULLDIST
-""""""""""""""""""""""
-
-Used as distance to plane for performing application-defined culling
-of individual primitives against a plane. When components of vertex
-elements are given this label, these values are assumed to be a
-float32 signed distance to a plane. Primitives will be completely
-discarded if the plane distance for all of the vertices in the
-primitive are < 0. If a vertex has a cull distance of NaN, that
-vertex counts as "out" (as if its < 0);
-The limits on both clip and cull distances are bound
-by the PIPE_MAX_CLIP_OR_CULL_DISTANCE_COUNT define which defines
-the maximum number of components that can be used to hold the
-distances and by the PIPE_MAX_CLIP_OR_CULL_DISTANCE_ELEMENT_COUNT
-which specifies the maximum number of registers which can be
-annotated with those semantics.
-
-
 TGSI_SEMANTIC_CLIPDIST
 """"""""""""""""""""""