Match test_root_module's deep-traversal assertion to gitdb's structure

gitdb's `async` submodule was removed back in 2014
(gitpython-developers/gitdb@bf942a9); only smmap remains. The leading
"gitdb / async" comment and the `assert len(rsmsp) >= 2` check
(loosened back in 2011 from `== 2` in 4a8bdce when smmap was added
to gitdb alongside async) are both stale.

Replace with an exact list-equality check on the expected paths in
traversal order. That order is also what later code in this function
assumes via positional indexing `rsmsp[0]`, `rsmsp[1]`.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: EliahKagan

test/test_submodule.py

@@ -508,9 +508,9 @@ def test_root_module(self, rwrepo):
         with rm.config_writer():
             pass
 
-        # Deep traversal gitdb / async.
+        # Deep traversal yields gitdb and its nested smmap.
         rsmsp = [sm.path for sm in rm.traverse()]
-        assert len(rsmsp) >= 2  # gitdb and async [and smmap], async being a child of gitdb.
+        assert rsmsp == ["git/ext/gitdb", "gitdb/ext/smmap"]
 
         # Cannot set the parent commit as root module's path didn't exist.
         self.assertRaises(ValueError, rm.set_parent_commit, "HEAD")