[Doc] Remove Input defaultValue syntax with a function

Closes #5354

docs/CreateEdit.md

@@ -1018,7 +1018,7 @@ To define default values, you can add a `initialValues` prop to form components
 The value of the form `initialValues` prop is an object, or a function returning an object, specifying default values for the created record. For instance:
 
 ```jsx
-const postDefaultValue = { created_at: new Date(), nb_views: 0 };
+const postDefaultValue = () => ({ id: uuid(), created_at: new Date(), nb_views: 0 });
 export const PostCreate = (props) => (
     <Create {...props}>
         <SimpleForm initialValues={postDefaultValue}>
@@ -1040,7 +1040,6 @@ Alternatively, you can specify a `defaultValue` prop directly in `<Input>` compo
 export const PostCreate = (props) => (
     <Create {...props}>
         <SimpleForm>
-            <TextInput source="id" defaultValue={React.useMemo(() => uuid(), [])} disabled />
             <TextInput source="title" />
             <RichTextInput source="body" />
             <NumberInput source="nb_views" defaultValue={0} />
@@ -1049,7 +1048,7 @@ export const PostCreate = (props) => (
 );
 ```
 
-**Tip**: For default values computed during the first render, or default values that are expensive to compute, use `React.useMemo` as in the example above.
+**Tip**: Per-input default values cannot be functions. For default values computed at render time, set the `initialValues` at the form level, as explained in the previous section. 
 
 ## Validation