Rollup merge of #118623 - haydonryan:master, r=workingjubilee

Improve std::fs::read_to_string example

Resolves  [#118621](rust-lang/rust#118621)

For the original code to succeed it requires address.txt to contain a socketaddress, however it is much easier to follow if this is just any strong - eg address could be a street address or just text.

Also changed the variable name from "foo" to something more meaningful as cargo clippy warns you against using foo as a placeholder.

```
$ cat main.rs
use std::fs;
use std::error::Error;

fn main() -> Result<(), Box<dyn Error>> {
    let addr: String = fs::read_to_string("address.txt")?.parse()?;
    println!("{}", addr);
    Ok(())
}

$ cat address.txt
123 rusty lane
san francisco 94999

$ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.00s
     Running `/home/haydon/workspace/rust-test-pr/tester/target/debug/tester`
123 rusty lane
san francisco 94999

```

Author: matthiaskrgr