Fix generated types in @react-native/virtualized-lists being used without opt-in (facebook#51246)

Summary:
Pull Request resolved: facebook#51246

Changelog: [General][Fixed] Fix generated types in react-native/virtualized-lists being used without opt-in

D71969602 introduces `exports` field to `package.json` files in `react-native` and `virtualized-lists`. In that diff, the `types` in `virtualized-lists` by default pointed to the new generated types without requiring the opt-in.

This fixes that by requiring the opt-in before using the generated types.

Reviewed By: huntie

Differential Revision: D74573321

fbshipit-source-id: fe05b0204a7200c1c91aac2614aa786bbbced2a5

Author: j-piasecki

packages/virtualized-lists/package.json

@@ -21,7 +21,8 @@
   },
   "exports": {
     ".": {
-      "types": "./types_generated/index.d.ts",
+      "react-native-strict-api": "./types_generated/index.d.ts",
+      "types": "./index.d.ts",
       "default": "./index.js"
     },
     "./*": {