Fix sidebars based on @beverleytalbott 's feedback on several pull requests

SIDEBAR.ftl.md

 
 There's more to building RESTful web services than is covered here. You can continue your exploration of Spring and REST with the following resources.
 
-### Getting Started Guides
+### Getting Started guides
 
 * [Consuming a RESTful Web Service][gs-consuming-rest]
 * [Building a Hypermedia-Driven REST Web Service][gs-rest-hateoas]

SIDEBAR.md

 
 There's more to building RESTful web services than is covered here. You can continue your exploration of Spring and REST with the following resources.
 
-### Getting Started Guides
+### Getting Started guides
 
 * [Consuming a RESTful Web Service][gs-consuming-rest]
 * [Building a Hypermedia-Driven REST Web Service][gs-rest-hateoas]