remove test_debug pipeline option

Follow-up to #133 (closed), which contains more details

AC:

• remove from pipeline-data: pipeline-data!262 (merged)
• remove from kernel-templates: !2276 (merged)
• remove from c10s .gitlab-ci.yml: redhat/centos-stream/src/kernel/centos-stream-10!282 (merged)
• remove from docs: documentation!555 (merged)
• remove from pipeline-definition code and variables: !2277 (merged)