chore(a11y): drop subsumed clock-health allowlist entries (#1717) (#1722)

## Summary

Drops the two stale `issue: 1717` entries from
`tests/a11y-allowlist.yaml`. Both were subsumed by PR #1720 (merged at
a344ae0a), which fixed the underlying color-contrast root causes on
`/analytics?tab=clock-health`:

| Removed entry | PR #1720 fix |
|---|---|
| `button[data-filter="all"]` (clock-health active filter) | P1: shared
`.btn-active-accent` class → 4.95:1 |
| `.skew-badge--no_clock` (count_max: 300) | P2: new
`--skew-badge-no-clock-bg` token → 7.56:1 |

Leaving these entries in place would mask any regression on those
surfaces, defeating the purpose of the gate.

## Scope

Config-only. Single file touched: `tests/a11y-allowlist.yaml`.

## TDD discipline

Per workspace AGENTS.md TDD exemption for config changes:
- **no test files modified**
- **config-only allowlist trim, CI green without test edits**

The local axe harness (`test-a11y-axe-1668.js`) cannot run in this
sandbox (Playwright/chromium boot issue — same constraint cited in PR
#1720). CI runs the same gate against the staging fixture and is the
source of truth.

## Verification

CI a11y-axe gate on this PR must show zero NEW violations on
`/analytics?tab=clock-health` after the entries are removed.

Partial fix for #1717 (will switch to "Fixes #1717" once CI confirms
zero violations on the clock-health tab post-removal).

Co-authored-by: Kpa-clawbot <bot@openclaw.local>

tests/a11y-allowlist.yaml

@@ -88,17 +88,6 @@ strict_unused: false
   rule: color-contrast
   issue: 1716
   expires_at: 2026-09-11
-- route: '/analytics?tab=clock-health'
-  selector: 'button[data-filter="all"]'
-  rule: color-contrast
-  issue: 1717
-  expires_at: 2026-09-11
-- route: '/analytics?tab=clock-health'
-  selector_pattern: '^\.clock-fleet-row--no_clock:nth-child\(\d+\) > td:nth-child\(3\) > \.skew-badge\.skew-badge--no_clock$'
-  count_max: 300
-  rule: color-contrast
-  issue: 1717
-  expires_at: 2026-10-09
 - route: '/analytics?tab=prefix-tool'
   selector: '#ptCheckBtn'
   rule: color-contrast