Fix Broken Link and Typo (#4763)

* Fix typo in angular/rxjs-basics/marble-diagrams

* Remove Marble Diagrams broken link

src/data/roadmaps/angular/content/101-rxjs-basics/102-marble-diagrams.md

@@ -4,6 +4,5 @@ Marble testing allows you to test asynchronous RxJS code synchronously and step-
 
 Visit the following resources to learn more:
 
-- [Angular Marble Testing: A Brief Introduction](https://www.altamira.ai/blog/angular-marble-testing-a-brief-introduction/)
-- [IUnderstanding Marble Diagrams for Reactive Streams](https://medium.com/@jshvarts/read-marble-diagrams-like-a-pro-3d72934d3ef5)
+- [Understanding Marble Diagrams for Reactive Streams](https://medium.com/@jshvarts/read-marble-diagrams-like-a-pro-3d72934d3ef5)
 - [Interactive Diagrams](https://rxmarbles.com/#from)