Merge pull request #3455 from Efrit16/patch-1

update CONTIBUTING.md

docs/CONTRIBUTING.md

@@ -4,7 +4,7 @@
 - Please read our [short and sweet coding guidelines](coding_guidelines.md).
 - For big changes such as adding new feature or refactoring, [file an issue first](https://github.com/Microsoft/AirSim/issues).
 - Use our [recommended development workflow](dev_workflow.md) to make changes and test it.
-- Use [usual steps](https://akrabat.com/the-beginners-guide-to-contributing-to-a-github-project/) to make contributions just like other GitHub projects. If you are not familiar with Git Branch-Rebase-Merge workflow, please [read this first](http://shitalshah.com/p/git-workflow-branch-rebase-squash-merge/).
+- Use [usual steps](https://www.dataschool.io/how-to-contribute-on-github/) to make contributions just like other GitHub projects. If you are not familiar with Git Branch-Rebase-Merge workflow, please [read this first](https://git-rebase.io/).
 
 ## Checklist
 - Use same style and formatting as rest of code even if it's not your preferred one.