Update setup-guides-for-microsoft-365.md

[v-troywarren]

Update MFA guide link.

https://go.microsoft.com/fwlink/?linkid=2258035

[learn-build-service-prod]

Learn Build status updates of commit 8b0c26f:

✅ Validation status: passed

File	Status	Preview URL	Details
microsoft-365/enterprise/setup-guides-for-microsoft-365.md	✅Succeeded

For more details, please refer to the build report.

For any questions, please:

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

[learn-build-service-prod]

Learn Build status updates of commit 49331fb:

✅ Validation status: passed

File	Status	Preview URL	Details
microsoft-365/enterprise/setup-guides-for-microsoft-365.md	✅Succeeded

For more details, please refer to the build report.

For any questions, please:

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