Do not opt-out fbsource/xplat/js/react-native-github/packages from CLANGFORMAT

Summary:
As we're working on C++ code for RNTester to integrate Fabric, we should enable CLANGFORMAT for the files over there.

Changelog:
[Internal] [Changed] - Enable CLANGFORMAT on fbsource/xplat/js/react-native-github/packages

Reviewed By: ShikaSD

Differential Revision: D32493605

fbshipit-source-id: 7b5d63f6d2fae1a1aa1e782738953c8cd2cdbe4b