nak/mark_lcssa_invariants: Invalidate divergence

Preserving this was resulting in validation errors like:
error: def->loop_invariant == BITSET_TEST(loop_invariance, def->index) (../src/compiler/nir/nir_validate.c:1890)

Fixes: 1d6082bf56 ("nouveau: switch to nir_metadata_divergence")
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36415>

src/nouveau/compiler/nak_nir_mark_lcssa_invariants.c

@@ -108,8 +108,7 @@ nak_nir_mark_lcssa_invariants(nir_shader *shader)
       nir_metadata_require(impl, nir_metadata_divergence);
 
       bool impl_progress = lower_cf_list(&b, &impl->body);
-      progress |= nir_progress(impl_progress, impl,
-                                         nir_metadata_control_flow | nir_metadata_divergence);
+      progress |= nir_progress(impl_progress, impl, nir_metadata_control_flow);
    }
 
    return progress;