Merge pull request marmelab#10302 from marmelab/doc-SimpleFormIterator-clone

[Doc] Remove outdated warning about `<SimpleFormIterator>` cloning its children

Author: djhi

docs/SimpleFormIterator.md

@@ -185,8 +185,6 @@ import { ArrayInput, SimpleFormIterator, DateInput, TextField, FormDataConsumer,
 </ArrayInput>
 ```
 
-**Caution**: `<SimpleFormIterator>` **clones** its children several times, as it needs to override their actual source for each record. If you use a custom Input element, make sure they accept a custom `source` prop. 
-
 ## `className`
 
 CSS classes passed to the root component.