Remove the PyTorch Moble iOS and Android folders

[cbilgin]

📚 The doc issue

Not exactly a doc issue but these need to be removed as well

• https://github.com/pytorch/ios-demo-app
• https://github.com/pytorch/pytorch/tree/main/android

Suggest a potential alternative/fix

No response

cc @mergennachin @byjlw

[larryliu0820]

Android demo app is removed