[native] Remove HelloWorld expo module
Summary:
Removed the scaffolded hello world module. It was only needed when other modules were not yet moved into the umbrella module.
Depends on D7963
Test Plan: This was not used anywhere, just ensured that the app still builds.
Reviewers: ashoat, atul, marcin
Reviewed By: ashoat
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D7964