fix(clean): Improving description for clean options

[Suryansh-Dey]

What does this PR try to resolve?

Closes issue #17129
Changes:

1. The find and replace of description as mentioned in issue description.
2. Used "only" in description as recommended by author here and also fixed the doc description.

How to test and review this PR?

Run man etc/man/cargo-clean.1

Run cargo run -- clean -h

Run cargo test clean::help and this passes

[rustbot]

Thanks for the pull request, and welcome! The Rust Project is excited to review your changes, and you should hear from @epage (or someone else) some time within the next two weeks.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

• @rustbot author: the review is finished, PR author should check the comments and take action accordingly
• @rustbot review: the author is ready for a review, this PR will be queued again in the reviewer's queue

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: @epage, @weihanglo
• @epage, @weihanglo expanded to epage, weihanglo
• Random selection from epage, weihanglo