Outdated Resource Links in README

[baharehforoughi]

I noticed that there are three outdated resource links at the end of the README file in the github-starter-course repository:
1- How to use GitHub branches
2-GitHub's Learning Lab
3-Education community forum
Unfortunately, these resources are no longer available or have been moved.

[egrace479]

The third still exists, but the first two do give 404's.