Remove Getting Started section

Closes gh-2341

Author: marcusdacoregio

spring-session-docs/modules/ROOT/nav.adoc

@@ -1,10 +1,4 @@
 * xref:whats-new.adoc[What's New]
-* xref:getting-started.adoc[Getting Started]
-** xref:getting-started/using-redis.adoc[Using Redis]
-** xref:getting-started/using-jdbc.adoc[Using JDBC]
-** xref:getting-started/using-mongodb.adoc[Using MongoDB]
-** xref:getting-started/using-hazelcast.adoc[Using Hazelcast]
-** xref:getting-started/using-custom-session-repository.adoc[Using Your Own Session Repository]
 * xref:samples.adoc[Samples & Guides (Start Here)]
 ** Boot Samples
 *** HttpSession