Remove legacy arch fallback from LayoutConformance (#56440)

Summary:

Remove the `isFabricUIManagerInstalled` guard and `UnimplementedLayoutConformance` fallback since the legacy architecture is no longer supported. Convert to Flow component syntax.

Changelog: [General][Removed] - Removed legacy architecture fallback from `LayoutConformance`

Differential Revision: D100817102

Author: javache

packages/eslint-plugin-react-native/utils.js

@@ -35,7 +35,7 @@ const publicAPIMapping = {
   },
   'Libraries/Components/LayoutConformance/LayoutConformance': {
     default: 'experimental_LayoutConformance',
-    types: ['LayoutConformanceProps'],
+    types: [],
   },
   'Libraries/Lists/FlatList': {
     default: 'FlatList',

packages/react-native/Libraries/Components/LayoutConformance/LayoutConformance.js

@@ -12,47 +12,23 @@ import StyleSheet from '../../StyleSheet/StyleSheet';
 import LayoutConformanceNativeComponent from './LayoutConformanceNativeComponent';
 import * as React from 'react';
 
-export type LayoutConformanceProps = Readonly<{
+export default component LayoutConformance(
   /**
    * strict: Layout in accordance with W3C spec, even when breaking
    * compatibility: Layout with the same behavior as previous versions of React Native
    */
   mode: 'strict' | 'compatibility',
-
   children: React.Node,
-}>;
-
-// We want a graceful fallback for apps using legacy arch, but need to know
-// ahead of time whether the component is available, so we test for global.
-// This does not correctly handle mixed arch apps (which is okay, since we just
-// degrade the error experience).
-const isFabricUIManagerInstalled = global?.nativeFabricUIManager != null;
-
-function LayoutConformance(props: LayoutConformanceProps): React.Node {
+) {
   return (
-    <LayoutConformanceNativeComponent {...props} style={styles.container} />
+    <LayoutConformanceNativeComponent
+      mode={mode}
+      children={children}
+      style={styles.container}
+    />
   );
 }
 
-function UnimplementedLayoutConformance(
-  props: LayoutConformanceProps,
-): React.Node {
-  if (__DEV__) {
-    const warnOnce = require('../../Utilities/warnOnce').default;
-
-    warnOnce(
-      'layoutconformance-unsupported',
-      '"LayoutConformance" is only supported in the New Architecture',
-    );
-  }
-
-  return props.children;
-}
-
-export default (isFabricUIManagerInstalled
-  ? LayoutConformance
-  : UnimplementedLayoutConformance) as component(...LayoutConformanceProps);
-
 const styles = StyleSheet.create({
   container: {
     display: 'contents',

packages/react-native/index.js.flow

@@ -64,7 +64,6 @@ export {default as InputAccessoryView} from './Libraries/Components/TextInput/In
 export type {KeyboardAvoidingViewProps} from './Libraries/Components/Keyboard/KeyboardAvoidingView';
 export {default as KeyboardAvoidingView} from './Libraries/Components/Keyboard/KeyboardAvoidingView';
 
-export type {LayoutConformanceProps} from './Libraries/Components/LayoutConformance/LayoutConformance';
 export {default as experimental_LayoutConformance} from './Libraries/Components/LayoutConformance/LayoutConformance';
 
 export type {