Update RHEL version for CNV installation

Author: apinnick

modules/virt-hardware-os-requirements.adoc

@@ -22,7 +22,7 @@ endif::[]
 * *Bare metal instances or servers offered by other cloud providers are not supported.*
 
 .CPU requirements
-* Supported by {op-system-base-full} 8
+* Supported by {op-system-base-full} 9
 * Support for Intel 64 or AMD64 CPU extensions
 * Intel VT or AMD-V hardware virtualization extensions enabled
 * NX (no execute) flag enabled