docs(api): fix broken link to "Services" guide

Nothing big. Simply a broken link to "Services".

> Nothing big.

It IS big, don't you ever forget it!

Closes angular#7101

Author: wojciechfornal

docs/content/api/index.ngdoc

@@ -6,7 +6,7 @@
 Welcome to the AngularJS API docs page. These pages contain the AngularJS reference materials for version <strong ng-bind="version"></strong>.
 
 The documentation is organized into **{@link guide/module modules}** which contain various components of an AngularJS application.
-These components are {@link guide/directive directives}, {@link guide/dev_guide.services services}, {@link guide/filter filters}, {@link guide/providers providers}, {@link guide/templates types}, global APIs and testing mocks.
+These components are {@link guide/directive directives}, {@link guide/services services}, {@link guide/filter filters}, {@link guide/providers providers}, {@link guide/templates types}, global APIs and testing mocks.
 
 <div class="alert alert-info">
 **Angular Namespaces `$` and `$$`**