amd/ci: add piglit failures due to a overzealous test

It's missing: https://gitlab.freedesktop.org/mesa/piglit/-/merge_requests/976

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32424>

src/amd/ci/radeonsi-raven-fails.txt

@@ -43,3 +43,6 @@ spec@!opengl 1.1@line-smooth-stipple,Fail
 spec@arb_viewport_array@display-list,Fail
 # since transition XORG -> WESTON
 glx@glx_arb_sync_control@waitformsc,Fail
+
+# This will be fixed by a piglit update
+spec@arb_uniform_buffer_object@referenced-by-shader,Fail

src/amd/ci/radeonsi-stoney-fails.txt

@@ -151,3 +151,6 @@ spec@arb_fragment_layer_viewport@layer-gs-writes-out-of-range,Fail
 # glcts update
 KHR-GLES3.clip_distance.coverage,Fail
 KHR-GLES3.cull_distance.functional,Fail
+
+# This will be fixed by a piglit update
+spec@arb_uniform_buffer_object@referenced-by-shader,Fail