Remove outdated SampleTurboCxxModuleLegacyImpl (#52412)

Summary:
Pull Request resolved: #52412

Changelog: [Internal]

The sample is from an outdated approach of enabling C++ Modules in RN which is not recommended anymore.

Prefer C++ Turbo Modules if you need to expose / access C or C++ APIs in RN apps:

https://reactnative.dev/docs/the-new-architecture/pure-cxx-modules

It is not included in any RNTester app at this time

Reviewed By: cortinico

Differential Revision: D77770455

fbshipit-source-id: 987c9f2b9ab4145a2f6a724aad12d8473957dbe8

Author: christophpurrer