docs: Wallet Example Clarification

[calldelegation]

Description

https://forum.fuel.network/t/module-wallet-abi-could-not-be-found/5116
Nick asked for clarification in the wallet example based on this inquiry in the forum.

TLDR:
It is unclear to the user that, when copying the example into their own Sway project, these are two separate projects and require a dependency declaration inside the forc.toml file.

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.