React Router: Clarify instructions for accessing sub-pages

[mhamza-khalid]

Because

This PR clarifies the instructions for navigating to specific profile pages (/profile/popeye and /profile/spinach) by manually entering the path in the URL. It aims to reduce confusion for users who may expect links or a navbar to access the children routes.

This PR

• Updated the lesson instructions in the .md file to clarify that users can access `/profile/popeye `and `/profile/spinach` by appending `/popeye` or `/spinach `to the `/profile` URL.

Issue

Closes #29031

Additional Information

No additional information.

Pull Request Requirements

• I have thoroughly read and understand The Odin Project curriculum contributing guide
• The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
• If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• If any lesson files are included in this PR, they follow the Layout Style Guide

[MaoShizhong]

Ignore the lint errors - they're out of scope for this PR.