Update signing guidance for /INTEGRITYCHECK files

[nbassett-MSFT]

The trusted signing service has a new name.

[learn-build-service-prod]

Learn Build status updates of commit 97af646:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
docs/build/reference/integritycheck-require-signature-check.md	⚠️Warning		Details

docs/build/reference/integritycheck-require-signature-check.md

• Line 20, Column 517: [Warning: hard-coded-locale - See documentation] Link 'https://azure.microsoft.com/en-us/products/artifact-signing' contains locale code 'en-us'. For localizability, remove 'en-us' from links to most Microsoft sites.

For more details, please refer to the build report.

Note: Your PR may contain errors or warnings or suggestions unrelated to the files you changed. This happens when external dependencies like GitHub alias, Microsoft alias, cross repo links are updated. Please use these instructions to resolve them.

[prmerger-automator]

@nbassett-MSFT : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[v-regandowner]

@TylerMSFT

Can you review the proposed changes?

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

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

[learn-build-service-prod]

Learn Build status updates of commit cd02fd6:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/build/reference/integritycheck-require-signature-check.md	✅Succeeded

For more details, please refer to the build report.