fix: handle nondeterminism in test (MystenLabs#18841)

## Description 

my guess is the modified signature byte is already 0 and does not need
modification. fix here is to deterministically flip the byte.
## Test plan 

How did you test the new or updated feature?

---

## Release notes

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- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] REST API:

crates/sui-e2e-tests/tests/passkey_e2e_tests.rs

@@ -303,7 +303,11 @@ async fn test_passkey_fails_to_verify_sig() {
     let test_cluster = TestClusterBuilder::new().build().await;
     let response = create_credential_and_sign_test_tx(&test_cluster, None, false, false).await;
     let mut modified_sig = response.user_sig_bytes.clone();
-    modified_sig[1] = 0x00;
+    if modified_sig[1] == 0x00 {
+        modified_sig[1] = 0x01;
+    } else {
+        modified_sig[1] = 0x00;
+    }
     let sig = GenericSignature::PasskeyAuthenticator(
         PasskeyAuthenticator::new_for_testing(
             response.authenticator_data,