fix(html-reporter): use h2 for non-expandable chip headers

[Simon Knott (Skn0tt)]

Quick follow up to #42149 - after that change, the Speedboard "Slowest Tests" chip header became plain text. Make non-expandable chip headers an h2 so they show up as a proper heading.

[github-actions]

Test results for "MCP"

8050 passed, 1284 skipped

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Merge workflow run.

[github-actions]

Test results for "tests 1"

10 flaky

⚠️ [chromium-library] › library/chromium/oopif.spec.ts:282 › should click `@frozen-time-library-chromium-linux`
⚠️ [chromium-library] › library/video.spec.ts:294 › screencast › should capture navigation `@frozen-time-library-chromium-linux`
⚠️ [chromium-library] › library/video.spec.ts:736 › screencast › should work with video+trace `@frozen-time-library-chromium-linux`
⚠️ [chromium-library] › library/beforeunload.spec.ts:130 › should support dismissing the dialog multiple times `@realtime-time-library-chromium-linux`
⚠️ [chromium-library] › library/video.spec.ts:356 › screencast › should work for popups `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/popup.spec.ts:260 › should not throw when click closes popup `@chromium-ubuntu-22.04-node22`
⚠️ [chromium-library] › library/video.spec.ts:699 › screencast › should capture full viewport on hidpi `@chromium-ubuntu-22.04-node22`
⚠️ [firefox-page] › page/page-event-request.spec.ts:181 › should return response body when Cross-Origin-Opener-Policy is set `@firefox-ubuntu-22.04-node20`
⚠️ [playwright-test] › ui-mode-test-output.spec.ts:118 › should collapse repeated console messages for test `@ubuntu-latest-node20`
⚠️ [playwright-test] › ui-mode-trace.spec.ts:715 › should indicate current test status `@windows-latest-node22`

51229 passed, 1190 skipped

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Merge workflow run.