Review GitHub Enterprise /environment deployments guidance

[ydaponte]

As per the ReadMe guidance, the GitHub Enterprise flag should be used when integrating with GitHub. For this particular configuration the AzDo organization needs to be in the same tenant as Azure. So the guidance needs to be updated to reflect:
1 - If you use GitHub Enterprise checkbox - then AzDo needs to be on the same tenant as Azure so the deployment doesn't fail
2 - If you don't use the GitHub Enterprise checkbox - then AzDo and Azure can leave on different tenants

DoD

• Correct ReadMe to reflect the above information