Enable `supported` features in unit tests.

This was a mistake -- `experimental` is supposed to always be paired with `supported`. This didn't cause any worng behavior now, because no actual behavior is gated behind the `supported` flag, but it would've been annoying to fix later.

PiperOrigin-RevId: 515363300
diff --git a/rs_bindings_from_cc/ir_testing.rs b/rs_bindings_from_cc/ir_testing.rs
index 390341c..0b23230 100644
--- a/rs_bindings_from_cc/ir_testing.rs
+++ b/rs_bindings_from_cc/ir_testing.rs
@@ -41,7 +41,8 @@
         /* current_target= */ target.clone(),
         /* top_level_item_ids= */ vec![],
         /* crate_root_path= */ None,
-        /* crubit_features= */ [(target, ir::CrubitFeature::Experimental)].into()
+        /* crubit_features= */
+        [(target, ir::CrubitFeature::Experimental | ir::CrubitFeature::Supported)].into(),
     )
 }