fix doc build on main (huggingface#1437)

Author: younesbelkada

trl/__init__.py

@@ -124,4 +124,10 @@
 else:
     import sys
 
-    sys.modules[__name__] = _LazyModule(__name__, globals()["__file__"], _import_structure, module_spec=__spec__)
+    sys.modules[__name__] = _LazyModule(
+        __name__,
+        globals()["__file__"],
+        _import_structure,
+        module_spec=__spec__,
+        extra_objects={"__version__": __version__},
+    )