tie translatewiki-puppet-validate to gallium

The translatewiki repository has submodules hosted on github and clone
them using either git or http protocols.

Whenever the job run on lanthanum, it will fail to clone the github
repository since that host does not have direct access to the internet.

Workaround is to tie it to gallium.

bug: 60164
Change-Id: I56119292695685d89d154d8315889c2a9064275c