Fix code in 'Use NavigationView instead of Pivot'

[artemious7]

The code was broken and incomplete. This fixes the code snippet.

[prmerger-automator]

@artemious7 : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[opbld32]

Learn Build status updates of commit 590928e:

✅ Validation status: passed

File	Status	Preview URL	Details
hub/apps/design/controls/pivot.md	✅Succeeded

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[prmerger-automator]

PRMerger Results

Issue	Description
File Change Percent	This PR contains file(s) with more than 20% file change.

[ShannonLeavitt]

@jwmsft - Could you review these changes?

IMPORTANT: When the changes are ready for publication, add a #sign-off comment to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

[prmerger-automator]

@artemious7 : Thanks for your contribution! The author(s) have been notified to review your proposed change.