Fix formatting on index.adoc

Author: rstoyanchev

src/docs/asciidoc/index.adoc

@@ -9,7 +9,7 @@ https://github.com/spring-projects/spring-framework/wiki[*Github Wiki*].
 ****
 
 [horizontal]
-<<overview.adoc#overview,*Overview*>> :: history, design philosophy,feedback,
+<<overview.adoc#overview,Overview>> :: history, design philosophy,feedback,
 getting started.
 <<core.adoc#spring-core,Core>> :: IoC container, Events, Resources, i18n, Validation,
 Data Binding, Type Conversion, SpEL, AOP.