In https://docs.openshift.com/container-platform/4.13/updating/updating-cluster-rhel-compute.html#rhel-compute-updating-minor_updating-cluster-rhel-compute section.

1. "Red Hat Enterprise Linux (RHEL) versions 8.4 and 8.5 are supported for RHEL compute machines."

should be 

"Red Hat Enterprise Linux (RHEL) versions 8.6 is supported for RHEL compute machines."
Since what QE tested is RHEL-8.6 worker in a 4.13 cluster.

2."On the machine that you run the Ansible playbooks, update the required repositories:


# subscription-manager repos --disable=rhocp-4.11-for-rhel-8-x86_64-rpms \
                             --disable=ansible-2.9-for-rhel-8-x86_64-rpms \
                             --enable=rhocp-4.12-for-rhel-8-x86_64-rpms"

which should be 
 # subscription-manager repos --disable=rhocp-4.12-for-rhel-8-x86_64-rpms \
                                                       --enable=rhocp-4.13-for-rhel-8-x86_64-rpms"


3. "On each RHEL compute node, update the required repositories:


# subscription-manager repos --disable=rhocp-4.11-for-rhel-8-x86_64-rpms \
                             --enable=rhocp-4.13-for-rhel-8-x86_64-rpms
" 
which should be 
# subscription-manager repos --disable=rhocp-4.12-for-rhel-8-x86_64-rpms \
                                                     --enable=rhocp-4.13-for-rhel-8-x86_64-rpms

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