[feature] cargo rm remove deps with a dash instead of an underscore

## Hi there,

### Context :
We take the `lazy_static` crate for the sake of the example.
When you use `cargo add` command to add the dependency but specify it with a dash instead of an underscore, you end up with this message `WARN: Added 'lazy_static' instead of 'lazy-static'`.
https://github.com/killercup/cargo-edit/blob/bd49ee227183fceb0b3cd488f0f239bfa58118bd/src/fetch.rs#L74-L78
This happens because the registry does correct this.

### Feature :
Now, when we want to remove a dependency but specify the wrong separator (dash or underscore), it errors out and exit.
Would it be possible to remove a dependency using another separator in `cargo rm` ? Or would it cost too much to implement ?

I didn't have the time to look deeper in the code, but I can try a PR.

Thanks for any further suggestions or approval.

Start with the cargo rm dependency lookup and removal path, then compare its name handling with fetch.rs lines 74-78, which are linked in the issue. Verify the behavior using the lazy_static/lazy-static example: specifying either separator should remove the dependency without an error.

Written by the indexing model from the issue text.