ci: Leave a note as to what might be going on with a test.

ci: Leave a note as to what might be going on with a test.

dEQP-GLES2.functional.clipping.triangle_vertex.clip_three.clip_neg_x_neg_z_and_pos_x_pos_z_and_neg_x_neg_y_pos_z
fails pretty strangely (given that we're passing everything else) and
there's an old VK-GL-CTS bug open about this test, and it's suspicious
that all the ARM drivers seem to have trouble with it.  I tried dropping
to -O0 on guilding that file in the CTS and it didn't help, though.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5419>