Put "Git Basics" at the top of the videos list

I send so many people to the video page who are just getting started with Git that it makes sense to have the "Git Basics" video go first. 

This PR will keep the "Git Basics" video at the top for ~1000 years. If we haven't all mastered Git as a universe by then, we have bigger problems :smile_cat: 

cc @github/training-team @cobyism