corrected typo in mac install documentation

[protenhan]

I corrected a typo in the mac os related MS Teams documentation.

[learn-build-service-prod]

Learn Build status updates of commit 93ecf17:

✅ Validation status: passed

File	Status	Preview URL	Details
Teams/new-teams-mac-install-prerequisites.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 5db2c38:

✅ Validation status: passed

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