Revert "tests(app): use compute_unbonding_height directly (review)"

This reverts commit d948eae.

crates/core/app/tests/app_can_undelegate_from_a_validator.rs

@@ -270,13 +270,13 @@ async fn app_can_undelegate_from_a_validator() -> anyhow::Result<()> {
     let post_undelegate_snapshot = storage.latest_snapshot();
 
     // Compute the height we expect to see this unbonding period finish.
-    let expected_end_of_unboding_period_height = post_undelegate_snapshot
-        .compute_unbonding_height(
-            &identity_key,
-            post_undelegate_snapshot.get_block_height().await?,
-        )
-        .await?
-        .expect("snapshot should have a block height");
+    let expected_end_of_unboding_period_height = {
+        // TODO(kate): right now the unbonding delay is calculated by using the start of the epoch
+        // as a beginning. so rather than...
+        // post_undelegated_height + UNBONDING_DELAY
+        // ...we write:
+        pre_undelegated_epoch.start_height + UNBONDING_DELAY
+    };
 
     // Show that we immediately receive unbonding tokens after undelegating.
     let undelegate_note: penumbra_shielded_pool::Note = {