Revise isGhes logic

[jww3]

Description

I'm fixing the logic within helper method isGhes to ensure that it doesn't misrecognize GitHub Enterprise Cloud instances as GHES instances.

Motivation and Context

https://github.com/newsroom/press-releases/data-residency-in-the-eu

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (add or update README or docs)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.