vulkan: Fix incorrect assert

You can have a group with 0 shaders in it. See also febe90e109
("vulkan: remove incorrect assert"). Fixes assertion failure while
compiling fossils/q2rtx/q2rtx-rt-pipeline.976f4ab1c0fee975.1.foz on
Intel platforms.

Fixes: e05a9b77b6 ("vulkan/runtime: split rt shaders hashing from compile")
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38318>

src/vulkan/runtime/vk_pipeline.c

@@ -3064,7 +3064,8 @@ vk_get_rt_pipeline_compile_info(struct vk_rt_pipeline_compile_info *info,
                                            group->stages, group->stage_count,
                                            group_linked_stages);
 
-      assert(group->stage_count > 0 && group->stage_count <= 3);
+      /* It is possible to have a group with 0 shaders. */
+      assert(group->stage_count <= 3);
    }
 
    if (libs_info != NULL) {