Removed links that returned 404 (#4331)

* [Princeton Algorithms, Part 2](https://www.coursera.org/course/algs4partII)
* [Machine Learning Mini Bootcamp](https://lambdaschool.com/free-course-machine-learning/)

Links were down as of 10/17/20

free-courses-en.md

@@ -264,7 +264,6 @@
 * [Object-Oriented programming with Java, part I](https://moocfi.github.io/courses/2013/programming-part-1/)
 * [Object-Oriented programming with Java, part II](https://moocfi.github.io/courses/2013/programming-part-2/)
 * [Princeton Algorithms, Part 1](https://www.coursera.org/course/algs4partI)
-* [Princeton Algorithms, Part 2](https://www.coursera.org/course/algs4partII)
 * [Problem Solving With Java](https://www.udacity.com/course/intro-to-java-programming--cs046) (Udacity)
 * [Spring 5 Core - An Ultimate Guide](https://www.udemy.com/learn-spring-5-core-from-scratch/) - Somnath Musib (Udemy)
 
@@ -349,7 +348,6 @@
 * [Google's Machine Learning Crash Course](https://developers.google.com/machine-learning/crash-course/)
 * [Intro to Machine Learning](https://www.kaggle.com/learn/intro-to-machine-learning) (Kaggle)
 * [Intro to Machine Learning Udacity](https://www.udacity.com/course/intro-to-machine-learning--ud120) (Udacity)
-* [Machine Learning Mini Bootcamp](https://lambdaschool.com/free-course-machine-learning/)
 * [Pattern Recognition and Machine Learning](https://www.microsoft.com/en-us/research/people/cmbishop/#!prml-book)
 * [Principles of Machine Learning By Microsoft](https://www.edx.org/course/principles-machine-learning-microsoft-dat203-2x-6)
 * [PyTorch tutorials by PyTorch.org](https://pytorch.org/tutorials)