docs: update import statement of ImageSizeControl component (#30704)

ImageSizeControl does not live in `@wordpress/components` but in
`@wordpress/block-editor`. The `__experimental` prefix is also needed.
See #17148#issuecomment-569528836

packages/block-editor/src/components/image-size-control/README.md

@@ -7,7 +7,7 @@ Allow users to control the width & height of an image.
 Render a ImageSizeControl.
 
 ```jsx
-import { ImageSizeControl } from '@wordpress/components';
+import { __experimentalImageSizeControl as ImageSizeControl } from '@wordpress/block-editor';
 import { withState } from '@wordpress/compose';
 
 const MyImageSizeControl = withState( {