[modin] Append to path to avoid namespace collision on development branches (#3621)

python/ray/__init__.py

@@ -47,7 +47,7 @@ except ImportError as e:
     raise
 
 modin_path = os.path.join(os.path.abspath(os.path.dirname(__file__)), "modin")
-sys.path.insert(0, modin_path)
+sys.path.append(modin_path)
 
 from ray.raylet import ObjectID, _config  # noqa: E402
 from ray.profiling import profile  # noqa: E402