fix(get-started): demo print '<' and '>' instead of '|'

[anc95]

I am a new learner of rust. I started my learning on https://www.rust-lang.org/learn/get-started

I found the second demo named A small Rust application should print

----------------------------
< Hello fellow Rustaceans! >
----------------------------

but not

----------------------------
| Hello fellow Rustaceans! |
----------------------------

so I raised this pr to fix this.