docs/features.txt: VK_EXT_separate_stencil_usage not exposed on RADV

Signed-off-by: Anthoine Bourgeois <anthoine.bourgeois@gmail.com>
Reported-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Fixes: 3d58ab7576d ("docs/features: Minor update extensions support")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7466>
diff --git a/docs/features.txt b/docs/features.txt
index 8a7cec4..9d966b5 100644
--- a/docs/features.txt
+++ b/docs/features.txt
@@ -468,7 +468,7 @@
   VK_EXT_host_query_reset                               DONE (anv, radv)
   VK_EXT_sampler_filter_minmax                          DONE (anv/gen9+, radv)
   VK_EXT_scalar_block_layout                            DONE (anv, radv/gfx7+)
-  VK_EXT_separate_stencil_usage                         DONE (anv, radv)
+  VK_EXT_separate_stencil_usage                         DONE (anv)
   VK_EXT_shader_viewport_index_layer                    DONE (anv, radv)
 
 Khronos extensions that are not part of any Vulkan version: