Remove outdated RHEL8 documentation (#13017)

Author: VannTen

README.md

@@ -89,13 +89,13 @@ vagrant up
 - **Flatcar Container Linux by Kinvolk**
 - **Debian** Bookworm, Bullseye, Trixie
 - **Ubuntu** 22.04, 24.04
-- **CentOS Stream / RHEL** [9, 10](docs/operating_systems/rhel.md#rhel-8)
+- **CentOS Stream / RHEL** 9, 10
 - **Fedora** 39, 40, 41, 42
 - **Fedora CoreOS** (see [fcos Note](docs/operating_systems/fcos.md))
 - **openSUSE** Leap 15.x/Tumbleweed
-- **Oracle Linux** [9, 10](docs/operating_systems/rhel.md#rhel-8)
-- **Alma Linux** [9, 10](docs/operating_systems/rhel.md#rhel-8)
-- **Rocky Linux** [9, 10](docs/operating_systems/rhel.md#rhel-8) (experimental in 10: see [Rocky Linux 10 notes](docs/operating_systems/rhel.md#rocky-linux-10))
+- **Oracle Linux** 9, 10
+- **Alma Linux** 9, 10
+- **Rocky Linux** 9, 10 (experimental in 10: see [Rocky Linux 10 notes](docs/operating_systems/rhel.md#rocky-linux-10))
 - **Kylin Linux Advanced Server V10** (experimental: see [kylin linux notes](docs/operating_systems/kylinlinux.md))
 - **Amazon Linux 2** (experimental: see [amazon linux notes](docs/operating_systems/amazonlinux.md))
 - **UOS Linux** (experimental: see [uos linux notes](docs/operating_systems/uoslinux.md))

docs/operating_systems/rhel.md

@@ -6,9 +6,9 @@ The documentation also applies to Red Hat derivatives, including Alma Linux, Roc
 
 The content of this section does not apply to open-source derivatives.
 
-In order to install packages via yum or dnf, RHEL 7/8 hosts are required to be registered for a valid Red Hat support subscription.
+In order to install packages via yum or dnf, RHEL hosts are required to be registered for a valid Red Hat support subscription.
 
-You can apply for a 1-year Development support subscription by creating a [Red Hat Developers](https://developers.redhat.com/) account. Be aware though that as the Red Hat Developers subscription is limited to only 1 year, it should not be used to register RHEL 7/8 hosts provisioned in Production environments.
+You can apply for a 1-year Development support subscription by creating a [Red Hat Developers](https://developers.redhat.com/) account. Be aware though that as the Red Hat Developers subscription is limited to only 1 year, it should not be used to register RHEL hosts provisioned in Production environments.
 
 Once you have a Red Hat support account, simply add the credentials to the Ansible inventory parameters `rh_subscription_username` and `rh_subscription_password` prior to deploying Kubespray. If your company has a Corporate Red Hat support account, then obtain an **Organization ID** and **Activation Key**, and add these to the Ansible inventory parameters `rh_subscription_org_id` and `rh_subscription_activation_key` instead of using your Red Hat support account credentials.
 
@@ -29,15 +29,7 @@ rh_subscription_role: "Red Hat Enterprise Server"
 rh_subscription_sla: "Self-Support"
 ```
 
-If the RHEL 8/9 hosts are already registered to a valid Red Hat support subscription via an alternative configuration management approach prior to the deployment of Kubespray, the successful RHEL `subscription-manager` status check will simply result in the RHEL subscription registration tasks being skipped.
-
-## RHEL 8
-
-If you have containers that are using iptables in the host network namespace (`hostNetwork=true`),
-you need to ensure they are using iptables-nft.
-An example how k8s do the autodetection can be found [in this PR](https://github.com/kubernetes/kubernetes/pull/82966)
-
-The kernel version is lower than the kubernetes 1.32 system validation, please refer to the [kernel requirements](../operations/kernel-requirements.md).
+If the RHEL hosts are already registered to a valid Red Hat support subscription via an alternative configuration management approach prior to the deployment of Kubespray, the successful RHEL `subscription-manager` status check will simply result in the RHEL subscription registration tasks being skipped.
 
 ## Rocky Linux 10