fix flatlist props being undefined in ios (#43141)

Summary:
When using Flatlist on iOS and Android its failing because props are undefined

The problem is described on https://github.com/facebook/react-native/issues/34783

![Captura de pantalla 2024-02-22 a las 4 13 11](https://github.com/facebook/react-native/assets/1161455/325738d9-2e49-44a0-bb6a-077b2e02e9cd)

![Captura de pantalla 2024-02-22 a las 4 14 58](https://github.com/facebook/react-native/assets/1161455/118f76e1-a818-428e-938e-123b55536b49)

Fixed by setting constructor before any statement and removing unnecessary props declaration at the top of the class.

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[GENERAL] [FIXED] - Fix undefined props crash in FlatList

Pull Request resolved: https://github.com/facebook/react-native/pull/43141

Reviewed By: javache

Differential Revision: D54069559

Pulled By: robhogan

fbshipit-source-id: b39cd9a273eb0279ed353f9efcb66a3c4ccf93b4

packages/react-native/Libraries/Lists/FlatList.js

@@ -308,7 +308,6 @@ export type Props<ItemT> = {
  * Also inherits [ScrollView Props](docs/scrollview.html#props), unless it is nested in another FlatList of same orientation.
  */
 class FlatList<ItemT> extends React.PureComponent<Props<ItemT>, void> {
-  props: Props<ItemT>;
   /**
    * Scrolls to the end of the content. May be janky without `getItemLayout` prop.
    */