Rollup merge of #33480 - birkenfeld:issue-33422, r=steveklabnik
Rollup merge of #33480 - birkenfeld:issue-33422, r=steveklabnik

book: fixup code in error handling tutorial

A few oversights happened while porting the example from docopt to getopts.  I retraced all the steps, fixing code and description as necessary.

Fixes: #33422

graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust