Fixed a repeated section title

Section 6 and a subsection of it had the exact same title - which can
lead to confusions if sections are reused and levels of subsections is
changed. Renamed the main chapter 6 to Installing SUSE Rancher Prime
cluster.

Author: chabowski

adoc/SAP-EIC-Harvester-main.adoc

@@ -168,7 +168,7 @@ include::SAP-EIC-Harvester.adoc[tag=harvester-VM-create]
 <?pdfpagebreak?>
 ++++
 
-== Installing {rancher}
+== Installing {rancher} cluster
 
 By now, you should have {harvester} installed and be able to deploy virtual machines.
 Next, we will focus on setting up {rancher}.

adoc/SAP-EIC-Main.adoc

@@ -116,7 +116,7 @@ include::SAP-EIC-SLEMicro.adoc[SLEMicro]
 <?pdfpagebreak?>
 ++++
 
-== Installing {rancher}
+== Installing {rancher} cluster
 
 By now you should have installed the operating system on every Kubernetes node.
 You are now ready to install a {rancher} cluster.