Fix typo in observer pattern (#3223)

content/roadmaps/104-angular/content/101-rxjs-basics/100-observable-pattern.md

@@ -1,8 +1,8 @@
-# Observable Pattern
+# Observer Pattern
 
 The observer pattern is a software design pattern in which an object, named the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods.
 
 Angular uses the Observer pattern which simply means — Observable objects are registered, and other objects observe (in Angular using the subscribe method) them and take action when the observable object is acted on in some way.
 
 <ResourceGroupTitle>Free Content</ResourceGroupTitle>
-<BadgeLink badgeText='Read' colorScheme='yellow' href='https://medium.com/fuzzycloud/angular-and-observable-4bf890b2a282'>Angular and Observable</BadgeLink>
+<BadgeLink badgeText='Read' colorScheme='yellow' href='https://medium.com/fuzzycloud/angular-and-observable-4bf890b2a282'>Angular and Observable</BadgeLink>