message: docs: fix angularfire2 hyperlink
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diff: @@ -15,7 +15,7 @@ For explanations on the individual techniques, visit the relevant NgModule pages
  Modules are a great way to organize an application and extend it with capabilities from external libraries.
  Angular libraries are NgModules, such as `FormsModule`, `HttpClientModule`, and `RouterModule`.
  -Many third-party libraries are available as NgModules such as [Material Design](https://material.angular.io), [Ionic](https://ionicframework.com), and [AngularFire2](https://github.com/angular/angularfire2.
  +Many third-party libraries are available as NgModules such as [Material Design](https://material.angular.io), [Ionic](https://ionicframework.com), and [AngularFire2](https://github.com/angular/angularfire2).
  NgModules consolidate components, directives, and pipes into cohesive blocks of functionality, each focused on a feature area, application business domain, workflow, or common collection of utilities.
  