Fix broken link to MockMvc documentation

Link to Test chapter of Spring Framework documentation is broken,
this commit fixes it.

Author: harcomaase

docs/modules/ROOT/pages/servlet/test/mockmvc/index.adoc

@@ -2,4 +2,4 @@
 = Spring MVC Test Integration
 :page-section-summary-toc: 1
 
-Spring Security provides comprehensive integration with https://docs.spring.io/spring/docs/current/spring-framework-reference/html/testing.html#spring-mvc-test-framework[Spring MVC Test]
+Spring Security provides comprehensive integration with https://docs.spring.io/spring-framework/reference/testing/mockmvc.html[Spring Testing MockMVC]