DesktopFormFactor.ExtensionPoint is invalid

[eloekset]

1. Clone the repo.
2. Open the MailCRM.sln from the Ex1\End folder.
3. Build the solution.

Result:
Severity Code Description Project File Line Suppression State Error The element 'DesktopFormFactor' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides' has invalid child element 'ExtensionPoint' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides'. List of possible elements expected: 'FunctionFile' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides'. MailCRM.Office C:\Rot\Office\Module3-OfficeAddins\Source\Ex1\End\MailCRM\MailCRM.Office\MailCRM.OfficeManifest\MailCRM.Office.xml 47