fix image build & update readme

[TomasTomecek]

ran into these while updating kernel

update README: convert-with-prep no longer exists

latest ansible no longer has debug callback

...which we used to get more convenient and verbose output

Let's just drop it, I assume it was moved to some collection.

[softwarefactory-project-zuul[bot]]

Build succeeded.

• pre-commit : SUCCESS in 2m 13s
• dist2src-tests : SUCCESS in 29m 16s
• dist2src-deployment-tests : SUCCESS in 17m 22s

[softwarefactory-project-zuul[bot]]

Build succeeded (gate pipeline).

• pre-commit : SUCCESS in 2m 06s

[TomasTomecek]

it indeed seems to be CentOS-stream8-specific

my F35:

$ ansible-doc -t callback -l | grep debug
debug                formatted stdout/stderr display   

ansible-2.9.27-1.fc35.noarch

Stream 8

Using /etc/ansible/ansible.cfg as config file
redirecting (type: callback) ansible.builtin.debug to ansible.posix.debug
ERROR! Invalid callback for stdout specified: debug

$ ansible-doc -t callback -l
default default Ansible screen output
junit   write playbook output to a JUnit file
minimal minimal Ansible screen output
oneline oneline Ansible screen output
tree    Save host events to files

no debug

$ dnf search ansible
ansible-collection-ansible-posix.noarch : Ansible Collection targeting POSIX and POSIX-ish platforms
ansible-collection-community-general.noarch : Modules and plugins supported by Ansible community
ansible-collection-community-mysql.noarch : MySQL collection for Ansible
ansible-collection-community-rabbitmq.noarch : RabbitMQ collection for Ansible
ansible-collection-microsoft-sql.noarch : The Ansible collection for Microsoft SQL Server management
ansible-collection-netbox-netbox.noarch : Netbox modules for Ansible
ansible-collection-redhat-rhel_mgmt.noarch : Ansible Collection of general system management and utility modules and other plugins
ansible-doc.noarch : Documentation for Ansible
ansible-freeipa-tests.noarch : ansible-freeipa tests
ansible-packaging.noarch : RPM packaging macros and generators for Ansible collections
ansible-pcp.noarch : Ansible Metric collection for Performance Co-Pilot
ansible-test.x86_64 : Tool for testing ansible plugin and module code
ansible-test.noarch : Tool for testing ansible plugin and module code

I presume it's somewhere in there