OCPBUGS-54903: Adding missing prereq to Azure Stack HUb docs

Author: dfitzmau

installing/installing_azure_stack_hub/ipi/installing-azure-stack-hub-default.adoc

@@ -18,6 +18,7 @@ While you can select `azure` when using the installation program to deploy a clu
 
 * You reviewed details about the xref:../../../architecture/architecture-installation.adoc#architecture-installation[{product-title} installation and update] processes.
 * You read the documentation on xref:../../../installing/overview/installing-preparing.adoc#installing-preparing[selecting a cluster installation method and preparing it for users].
+* You have installed Azure Stack Hub version 2008 or later. 
 * You xref:../../../installing/installing_azure_stack_hub/installing-azure-stack-hub-account.adoc#installing-azure-stack-hub-account[configured an Azure Stack Hub account] to host the cluster.
 * If you use a firewall, you xref:../../../installing/install_config/configuring-firewall.adoc#configuring-firewall[configured it to allow the sites] that your cluster requires access to.
 * You verified that you have approximately 16 GB of local disk space. Installing the cluster requires that you download the {op-system} virtual hard drive (VHD) cluster image and upload it to your Azure Stack Hub environment so that it is accessible during deployment. Decompressing the VHD files requires this amount of local disk space.

installing/installing_azure_stack_hub/ipi/installing-azure-stack-hub-network-customizations.adoc

@@ -17,6 +17,7 @@ While you can select `azure` when using the installation program to deploy a clu
 
 * You reviewed details about the xref:../../../architecture/architecture-installation.adoc#architecture-installation[{product-title} installation and update] processes.
 * You read the documentation on xref:../../../installing/overview/installing-preparing.adoc#installing-preparing[selecting a cluster installation method and preparing it for users].
+* You have installed Azure Stack Hub version 2008 or later. 
 * You xref:../../../installing/installing_azure_stack_hub/installing-azure-stack-hub-account.adoc#installing-azure-stack-hub-account[configured an Azure Stack Hub account] to host the cluster.
 * If you use a firewall, you xref:../../../installing/install_config/configuring-firewall.adoc#configuring-firewall[configured it to allow the sites] that your cluster requires access to.
 * You verified that you have approximately 16 GB of local disk space. Installing the cluster requires that you download the {op-system} virtual hard drive (VHD) cluster image and upload it to your Azure Stack Hub environment so that it is accessible during deployment. Decompressing the VHD files requires this amount of local disk space.

installing/installing_azure_stack_hub/upi/installing-azure-stack-hub-user-infra.adoc

@@ -20,6 +20,7 @@ The steps for performing a user-provisioned infrastructure installation are prov
 
 * You reviewed details about the xref:../../../architecture/architecture-installation.adoc#architecture-installation[{product-title} installation and update] processes.
 * You read the documentation on xref:../../../installing/overview/installing-preparing.adoc#installing-preparing[selecting a cluster installation method and preparing it for users].
+* You have installed Azure Stack Hub version 2008 or later. 
 * You xref:../../../installing/installing_azure_stack_hub/installing-azure-stack-hub-account.adoc#installing-azure-stack-hub-account[configured an Azure Stack Hub account] to host the cluster.
 * You downloaded the Azure CLI and installed it on your computer. See link:https://docs.microsoft.com/en-us/cli/azure/install-azure-cli?view=azure-cli-latest[Install the Azure CLI] in the Azure documentation. The documentation below was tested using version `2.28.0` of the Azure CLI. Azure CLI commands might perform differently based on the version you use.
 * If you use a firewall and plan to use the Telemetry service, you xref:../../../installing/install_config/configuring-firewall.adoc#configuring-firewall[configured the firewall to allow the sites] that your cluster requires access to.