Use HelloWorld as the default debug target

[JoelYYoung]

Summary

• make bin/hello the default VS Code F5 target
• remove the Assignment 1 input argument from the default configuration
• keep assignment-specific program and argument selection in the Wiki

Verification

• Dockerfile validation passes
• bin/hello runs without arguments and prints Hello World!

The corresponding Wiki documentation was updated in one location only: Installation of Docker, VSCode and its extensions, section 2.1.