Fix issues in forc add/remove --help

[ironcev]

Description

Fixes #7557 by adding doc-comment to add and remove commands and removing typos and wrong comments.

• Fixes Forc add and remove commands do not have help and have errors in examples #7557.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[ironcev]

👍

[cursor]

PR Summary

Low Risk
Help/documentation-only string and comment changes; no behavior or dependency-modification logic is touched.

Overview
Fixes forc add/forc remove CLI help text by correcting example descriptions (e.g., "Add a dependencies" -> "Add a dependency", and "Add" -> "Remove" in remove).

Replaces misleading inline comments with rustdoc doc comments for both commands so --help/generated docs describe modifying Forc.toml dependencies accurately.

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