Add GitLab host to 2FA QR and manual info
What does this MR do?
Adds helpful context to the 2FA 'Account' field. User requested this in https://gitlab.zendesk.com/agent/tickets/43738. Currently, when a user scans the QR code, the 'Account' or text that appears in the code generator app simply includes the user's email. This isn't very descriptive and among a list of other 2FA accounts, can't be differentiated.
This MR adds the GitLab host/URL before the user's email - gitlab.example.com - user@example.com. It also adds this same text to the 'Account' field in the manual instructions