docs($rootScope.Scope): remove obsolete line, and link to guide

The removed line pointed to a removed example. Re-adding the example
would have been of questionable value, as it introduced several
concepts without context. It's therefore better to link to the guide,
which provides a better introduction.

Closes #12167

Author: Narretz

src/ng/rootScope.js

@@ -108,12 +108,9 @@ function $RootScopeProvider() {
      * A root scope can be retrieved using the {@link ng.$rootScope $rootScope} key from the
      * {@link auto.$injector $injector}. Child scopes are created using the
      * {@link ng.$rootScope.Scope#$new $new()} method. (Most scopes are created automatically when
-     * compiled HTML template is executed.)
+     * compiled HTML template is executed.) See also the {@link guide/scope Scopes guide} for
+     * an in-depth introduction and usage examples.
      *
-     * Here is a simple scope snippet to show how you can interact with the scope.
-     * ```html
-     * <file src="./test/ng/rootScopeSpec.js" tag="docs1" />
-     * ```
      *
      * # Inheritance
      * A scope can inherit from a parent scope, as in this example: