Clean up Command factory/constructor documentation

[rzblue]

https://docs.wpilib.org/en/2023_a/docs/software/commandbased/commands.html

Currently there is an inconsistent/incomplete mix of using the constructor and using the factory method inside the code blocks, while the documentation refers to the factory methods.

The code blocks/RLIs also use the factory methods of Subsystem in the context of a subsystem (eg using this.runOnce) which can be confusing without the surrounding context.