Update auth caption for Entra ID (formerly AAD)

[j-mok]

There's been a rebranding of Azure Active Directory to Microsoft Entra ID. This PR reflects this change in the most user-facing spot, that is the log-in page, but I think both documentation and the AzureAd module will also need at least some rebranding too.

[vc-ci]

Reveiw task created: https://virtocommerce.atlassian.net/browse/PT-14796