Clean up list of application examples in Qt 6.10.

Application examples should be complete applications with a (hypothetical) use case. As the application example category is shown first in Qt Creator, they should be visually pleasing, adhere to best practices, and compile and run _without any warnings.

Suggested changes:

• Getting Started Programming with Qt Quick
  • This is a tutorial, not an (application) example
  • -> Move to Other category
• Qt Quick Demo - RESTful API client
  • Name indicates the technology, not the purpose of the app.
  • Has a rather weak hypothetical use case.
  • -> Better fits to Networking category
• Window Embedding
  • This is a technology demo, not an example with a use case
  • -> Move to Graphics category
• QtJenny: Generating C++ proxy classes to access Android APIs
  • This is a technology demo, not an example with a use case
  • -> Move to Mobile category