docs(ngIf): update out-of-date link

Author: jesselpalmer

src/ng/directive/ngIf.js

@@ -19,7 +19,7 @@
  * Note that when an element is removed using `ngIf` its scope is destroyed and a new scope
  * is created when the element is restored.  The scope created within `ngIf` inherits from
  * its parent scope using
- * [prototypal inheritance](https://github.com/angular/angular.js/wiki/The-Nuances-of-Scope-Prototypal-Inheritance).
+ * [prototypal inheritance](https://github.com/angular/angular.js/wiki/Understanding-Scopes#javascript-prototypal-inheritance).
  * An important implication of this is if `ngModel` is used within `ngIf` to bind to
  * a javascript primitive defined in the parent scope. In this case any modifications made to the
  * variable within the child scope will override (hide) the value in the parent scope.