The Linking and BackHandler components are now both supported by react-native-web (#3494)

so there's no need to supply dummy replacements.

src/PlatformHelpers.web.js

@@ -1,9 +1,3 @@
-export const Linking = {
-  addEventListener: () => {},
-  removeEventListener: () => {},
-  getInitialURL: () => Promise.reject('Unsupported platform'),
-};
+import { BackHandler } from 'react-native';
 
-export const BackHandler = {
-  addEventListener: () => {},
-};
+export { BackHandler };