test(ci): clean up auto-heal v1->v2 integration test debt (#1461)

Delete tests/integration/test_auto_heal_workflow.py. The file was
written for v1 (workflow name 'Auto-heal', ALLOW_RE inline regex,
references to scripts/auto_heal_categorize.py and the v1-only
helpers). It had 19 of 36 tests failing on main before PR #1452
landed and added no coverage v2 didn't already have.

The v2 surface is fully exercised by:

  * tests/unit/test_autoheal_workflow_yaml.py (43 assertions on
    workflow YAML: capability tokens, cordon-zone wording, pinned
    SHAs, permission profile, etc.)
  * tests/integration/test_autoheal_workflow.py (no underscore;
    drives scripts/auto_heal_v2_run.py end-to-end: triage,
    kill-switch, bandit, log)

Operator pickup item 2 from the v2 audit a3c4b51caf65f89f5.

Co-authored-by: auto-heal-fixup <auto-heal-fixup@bernstein.local>

Author: chernistry