Remove quotes from How-to in ref doc

Issue gh-499

docs/src/docs/asciidoc/how-to.adoc

@@ -1,5 +1,5 @@
 [[how-to]]
-= "How-to" Guides
+= How-to Guides
 
 [[how-to-overview]]
 == List of Guides

docs/src/docs/asciidoc/index.adoc

@@ -12,4 +12,4 @@ xref:getting-started.adoc[Getting Started] :: System requirements, dependencies
 xref:configuration-model.adoc[Configuration Model] :: Default configuration and customizing the configuration
 xref:core-model-components.adoc[Core Model / Components] :: Core domain model and component interfaces
 xref:protocol-endpoints.adoc[Protocol Endpoints] :: OAuth2 and OpenID Connect 1.0 protocol endpoint implementations
-xref:how-to.adoc["How-to" Guides] :: Guides to get the most from Spring Authorization Server
+xref:how-to.adoc[How-to Guides] :: Guides to get the most from Spring Authorization Server