Fix react-native-git-upgrade cache busting

Summary:
**Motivation**

This PR fixes #12420.

For the first time, the version 0.41.2 includes a change in the generator (see #12162). The [require cache busting](https://github.com/facebook/react-native/blob/master/react-native-git-upgrade/cliEntry.js#L157-L163) of `react-native-git-upgrade`, designed to face this situation , was ineffective.

The entry in `require.cache` is the file path including the `.js` extension. We have to delete this entry with the same key.

**Test plan**

- Publish `react-native-git-upgrade` to Sinopia,
- Follow the reproduction steps of #12420
- 👉 The name of the app shouldn't be changed
Closes https://github.com/facebook/react-native/pull/12422

Differential Revision: D4585549

Pulled By: mkonicek

fbshipit-source-id: 508ac925c17d02b7739d47f9351a5aa336589f2e