hello-world: Update GETTING_STARTED.md to match simplified exercise (#266)
hello-world: Update GETTING_STARTED.md to match simplified exercise (#266)

Closes #265.
sacherjj/rust,exercism/xrust,sacherjj/rust,exercism/xrust,sacherjj/rust,petertseng/exercism-rust,petertseng/exercism-rust,petertseng/exercism-rust