Remove RN metro-config migration checks (#57648)

Summary:
Pull Request resolved: #57648

Legacy check, clean up.

Changelog: [Internal]

___

Differential Revision: D113396915

fbshipit-source-id: 697b65f1a02a98949f490b2cc94d0864d52d1472

Author: huntie

packages/community-cli-plugin/src/utils/loadMetroConfig.js

@@ -96,8 +96,6 @@ export default async function loadMetroConfig(
 
   // Get the RN defaults before our customisations
   const defaultConfig = RNMetroConfig.getDefaultConfig(ctx.root);
-  // Unflag the config as being loaded - it must be loaded again in userland.
-  global.__REACT_NATIVE_METRO_CONFIG_LOADED = false;
 
   // Add our defaults to `@react-native/metro-config` before the user config
   // loads them.
@@ -119,20 +117,6 @@ export default async function loadMetroConfig(
 
   debug(`Reading Metro config from ${projectConfig.filepath}`);
 
-  if (!global.__REACT_NATIVE_METRO_CONFIG_LOADED) {
-    const warning = `
-=================================================================================================
-From React Native 0.73, your project's Metro config should extend '@react-native/metro-config'
-or it will fail to build. Please copy the template at:
-https://github.com/react-native-community/template/blob/main/template/metro.config.js
-This warning will be removed in future (https://github.com/facebook/metro/issues/1018).
-=================================================================================================
-    `;
-
-    for (const line of warning.trim().split('\n')) {
-      console.warn(line);
-    }
-  }
   return loadConfig({
     cwd,
     ...options,

packages/metro-config/src/index.flow.js

@@ -99,9 +99,6 @@ export function getDefaultConfig(projectRoot: string): ConfigT {
     watchFolders: [],
   };
 
-  // Set global hook so that the CLI can detect when this config has been loaded
-  global.__REACT_NATIVE_METRO_CONFIG_LOADED = true;
-
   const metroDefaults = getBaseConfig.getDefaultValues(projectRoot);
 
   return mergeConfig(metroDefaults, reactNativeDefaults, frameworkDefaults);