Remove dead links on `courses.md` and `readings.md`

[micalevisk]

After running

lychee https://raw.githubusercontent.com/ossu/computer-science/835c2c101d7c27ac8beb93dfb8af9aab22a85565/extras/courses.md

lychee https://raw.githubusercontent.com/ossu/computer-science/835c2c101d7c27ac8beb93dfb8af9aab22a85565/extras/readings.md

I've found the following dead links

• computer-science/extras/courses.md

  Line 81 in 835c2c1

  [Processing Big Data with Azure HDInsight](https://www.edx.org/course/processing-big-data-azure-hdinsight-microsoft-dat202-1x-0)| 5 weeks | 3-4 hours/week

• computer-science/extras/readings.md

  Line 36 in 835c2c1

  [Applied Discrete Structures](http://faculty.uml.edu/klevasseur/ads2/) | Alan Doerr, Ken Levasseur

[waciumawanjohi]

The entire faculty subdomain for UMass Lowell is down. I wonder if that's an error. There are still live links from Levasseur's entry in the UMass directory to that faculty site:
https://www.uml.edu/profile/kenneth_levasseur

[waciumawanjohi]

Big Data course has been removed from EDx. Making a commit to remove it.

Thanks for the heads up!