Update licensing-service-plan-reference.md

Hello everyone, 

Customer complained that Viva Learning Seeded (b76fb638-6ba6-402a-b9f9-83d28acb3d86) is missing from Office 365 E5 - EnterprisePremium license service plan details. When exporting the CSV the license is also missing from it.

We didn't noticed if any other service is missing, but we are sure that Viva Learning Seeded should be there.

Thank you.

Pedro Ribeiro

Author: peribeir-msft