chore: remove Jira/SRVKP references from PAC repository

[chmouel]

Context

PAC is moving to the tektoncd community which uses GitHub issues natively. All Jira/SRVKP integrations should be removed.

Files to remove or update

File	Action
.tekton/jira.yaml	Delete — entire PipelineRun for /jira-create command
hack/pr-ci/jira.py	Delete — JiraClient + GeminiJiraGenerator
hack/pr-ci/config.py	Remove JIRA_CUSTOM_FIELDS and jira config fields (lines 11–89)
hack/pr-ci/main.py	Remove run_jira_create() function and /jira-create handler (lines 235–369)
hack/generate-releasenotes.py	Remove SRVKP-\d+ regex (line 40) and Jira-formatted output
.github/pull_request_template.md	Remove "Linked Jira" section (lines 3, 5, 11)
AGENTS.md	Remove Jira skills references from Skills section
.claude/skills/jira-ticket/	Delete entire skill directory
.claude/skills/commit-message/references/jira-lookup.md	Delete

Notes

• The /jira-create bot command will no longer be available after these changes.
• Release notes generation in hack/generate-releasenotes.py should be updated to reference GitHub issue numbers instead of SRVKP tickets.
• PR template should be updated to reference GitHub issues only.