According to the documentation, to leverage managed identities:
Set the Connection property to the name of a shared prefix for multiple application settings, together defining identity-based authentication. This method is supported when using version 3.3.x or higher of the extension.
Connection does not exist on com.microsoft.azure.functions.annotation@EventGridOutput so therefore cannot be set.
According to the documentation, to leverage managed identities:
Connectiondoes not exist oncom.microsoft.azure.functions.annotation@EventGridOutputso therefore cannot be set.