docs: Update sample directory navigation commands in READMEs.

[nan-yu]

Description

Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.

List which issues are fixed by this PR. For larger changes, raising an issue first helps reduce redundant work.

Pre-launch Checklist

• I signed the CLA.
• I read the Contributors Guide.
• I read the Style Guide.
• I have added updates to the CHANGELOG.
• I updated/added relevant documentation.
• My code changes (if any) have tests.

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[gemini-code-assist]

Code Review

The pull request effectively updates the navigation commands in the README.md files for the contact_lookup and restaurant_finder samples. These changes are accurate and improve the clarity of the documentation, making it easier for users to navigate to the correct sample directories. However, the pre-launch checklist in the PR description is not fully completed, which is a violation of the repository's style guide (lines 18-20). Specifically, the items "I read the [Contributors Guide].", "I read the [Style Guide].", and "I have added updates to the [CHANGELOG]." are unchecked. Adhering to the full checklist is a requirement for all pull requests.