message: docs: add small clarity around navigationCancel
  Add small clarity to sentence in documentation for navigation cancel event
  to indicate that router guards returning false or urlTree is only one of
  several reasons a NavigationCancel event happens.
  fixes
  PR Close
diff: @@ -134,7 +134,7 @@ export class NavigationEnd extends RouterEvent {
  /**
  * An event triggered when a navigation is canceled, directly or indirectly.
  - * This can happen when a route guard
  + * This can happen for several reasons including when a route guard
  * returns `false` or initiates a redirect by returning a `UrlTree`.
  *
  * @see `NavigationStart`
  