Fix quick start guide println

[zadjadr]

Otherwise you get this error:

error: invalid format string: expected `'}'`, found `'?'`
  --> src/main.rs:21:47
   |
21 |         println!("upstream peer is: {:upstream?}");
   |                                     -         ^ expected `'}'` in format string
   |                                     |
   |                                     because of this opening brace
   |
   = note: if you intended to print `{`, you can escape it using `{{`

error: could not compile `pnginx` (bin "pnginx") due to 1 previous error

[1000Delta]

LGTM

[andrewhavck]

Thanks, we forgot to sync a commit last week that fixed this, it is synced now. Closing.