e2e: Fix race condition in test_non_fastforward_identity_doc

Fixes an intermittent failure caused by a race condition with background
gossip messages.

Previously Eve's `RefsAnnounced` message could be processed by Bob
after the test updated the identity document to include Alice-Laptop
as a delegate. This caused Bob to unexpectedly fetch the issue in the
background, failing the `!has_issue` assertion.

We now explicitly wait for Bob to receive Eve's announcement before
updating the identity document.

crates/radicle-node/src/tests/e2e.rs

@@ -1725,6 +1725,7 @@ fn test_non_fastforward_identity_doc() {
     let mut alice = alice.spawn();
     let mut alice_laptop = alice_laptop.spawn();
     let mut bob = bob.spawn();
+    let bob_events = bob.handle.events();
     let mut eve = eve.spawn();
 
     let has_issue = |node: &NodeHandle<MockSigner>, issue: &cob::ObjectId| -> bool {
@@ -1770,6 +1771,13 @@ fn test_non_fastforward_identity_doc() {
         .unwrap();
     assert!(has_issue(&eve, &issue));
 
+    bob_events
+        .wait(
+            |e| matches!(e, Event::RefsAnnounced { nid, .. } if *nid == eve.id).then_some(()),
+            DEFAULT_TIMEOUT,
+        )
+        .unwrap();
+
     // Alice updates the identity of the document to include her laptop
     let (prev, next) = {
         let repo = alice.storage.repository(rid).unwrap();