Normalize udacity listings (#3409)

Some of our Udacity listings added '(Udacity)' as and access note. This PR makes the practice uniform. We can consider other platforms case by case. In general, I feel that when the platform offers additional services that make it matter what platform a course is on, the addition of an access note is useful.

Comments welcome on appropriateness of  the access notes.

free-courses-en.md

@@ -135,7 +135,7 @@
 
 ### Cuda
 
-* [Intro to Parallel Programming Using CUDA to Harness the Power of GPUs](https://www.udacity.com/course/intro-to-parallel-programming--cs344)
+* [Intro to Parallel Programming Using CUDA to Harness the Power of GPUs](https://www.udacity.com/course/intro-to-parallel-programming--cs344) (Udacity)
 
 
 ### Data Science
@@ -161,7 +161,7 @@
 * [Practical Deep Learning For Coders taught](http://www.fast.ai) - Jeremy Howard
 * [Self-Paced Courses for Deep Learning](https://developer.nvidia.com/deep-learning-courses)
 * [Unsupervised Feature Learning and Deep Learning](http://deeplearning.stanford.edu/tutorial)
-* [What is Deep Learning](https://www.udacity.com/course/deep-learning--ud730)
+* [What is Deep Learning](https://www.udacity.com/course/deep-learning--ud730) (Udacity)
 
 
 ### Git
@@ -223,7 +223,7 @@
 * [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)
+* [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)
 
 
@@ -433,7 +433,7 @@
 ### Theory
 
 * [Automata Theory](https://lagunita.stanford.edu/courses/course-v1:ComputerScience+Automata+Fall2016/about)
-* [Udacity: Intro to Theoretical Computer Science](https://www.udacity.com/course/intro-to-theoretical-computer-science--cs313)
+* [Intro to Theoretical Computer Science](https://www.udacity.com/course/intro-to-theoretical-computer-science--cs313) (Udacity)
 
 
 ### TypeScript