Bump github.com/Azure/azure-sdk-for-go/sdk/data/azcosmos from 1.1.0 to 1.2.0 in /backend in the azure-sdk-for-go group

Bump github.com/Azure/azure-sdk-for-go/sdk/data/azcosmos from 1.1.0 to 1.2.0 in /backend in the azure-sdk-for-go group #1919