fix(move_semantics2): fix line number comment

[akgerber]

Commit fef8314 added three lines of comments, which left the line numbers expected to stay unchanged mentioned on line 2 out of date.

[akgerber]

Also note that techniques 2 and 3 suggested in the hint do not produce the expected output per fef8314:

So, `vec0` is passed into the `fill_vec` function as an argument. In Rust,
when an argument is passed to a function and it's not explicitly returned,
you can't use the original variable anymore. We call this "moving" a variable.
Variables that are moved into a function (or block scope) and aren't explicitly
returned get "dropped" at the end of that function. This is also what happens here.
There's a few ways to fix this, try them all if you want:
1. Make another, separate version of the data that's in `vec0` and pass that
   to `fill_vec` instead.
2. Make `fill_vec` borrow its argument instead of taking ownership of it,
   and then copy the data within the function in order to return an owned
   `Vec<i32>`
3. Make `fill_vec` *mutably* borrow a reference to its argument (which will need to be
   mutable), modify it directly, then not return anything. Then you can get rid
   of `vec1` entirely -- note that this will change what gets printed by the
   first `println!

[shadows-withal]

@all-contributors please add @akgerber for content

[allcontributors]

@shadows-withal

I've put up a pull request to add @akgerber! 🎉