Update connect-workday.md with GCC URI

[preetgill9]

Document is missing details for "Redirection URI" for GCC customers, hence GCC customers are getting confused and try to use the commercial or GCC High URI that is provided in the document. Adding the URI for GCC customers will help them use the correct URI for GCC and reduce support cases for CSS.

Currently, doc only shares the URI for Commercial and GCC High Customers, URI details for GCC customers is missing. So I added the URI details for GCC as well.

Line added to the doc: For US Government GCC customers, enter the following value: https://portal.cloudappsecuritygov.com/api/oauth/connect

[prmerger-automator[bot]]

@preetgill9 : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[learn-build-service-prod[bot]]

Learn Build status updates of commit fd1be90:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
CloudAppSecurityDocs/connect-workday.md	:white_check_mark:Succeeded

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[dcurwin]

@preetgill9 - You opened this PR in the public repo. I'm closing it - can you please open it in the private repo instead?

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