Fix multisig address generation in multisig.py example (#8668)

AccountAddress class is missing `from_multisig_schema` function, use `from_multi_ed25519` instead.

```
multisig_address = AccountAddress.from_multisig_schema(
        [alice.public_key(), bob.public_key(), chad.public_key()], threshold
    )
```

ecosystem/python/sdk/examples/multisig.py

@@ -59,9 +59,7 @@ def wait():
         [alice.public_key(), bob.public_key(), chad.public_key()], threshold
     )
 
-    multisig_address = AccountAddress.from_multisig_schema(
-        [alice.public_key(), bob.public_key(), chad.public_key()], threshold
-    )
+    multisig_address = AccountAddress.from_multi_ed25519(multisig_public_key)
 
     print("\n=== 2-of-3 Multisig account ===")
     print(f"Account public key: {multisig_public_key}")