Fix typo in Dispatcher.h (#89045)

Fix typo in Dispatcher.h: hamespace -> namespace
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89045
Approved by: https://github.com/bdhirsh, https://github.com/kit1980
diff --git a/aten/src/ATen/core/dispatch/Dispatcher.h b/aten/src/ATen/core/dispatch/Dispatcher.h
index 6e1c7d7..5af8ef1 100644
--- a/aten/src/ATen/core/dispatch/Dispatcher.h
+++ b/aten/src/ATen/core/dispatch/Dispatcher.h
@@ -735,4 +735,4 @@
   }
 };
 
-} // hamespace std
+} // namespace std