chore(deps): update dependency @open-wc/testing to v4 #4254

Job	Run time
Verify changes (lit-element)	42s
Verify changes (lit-element-ts-esbuild)	45s
Verify changes (lit-element-ts-tsc)	40s
Verify changes (html-test)	51s
Verify changes (preact-htm)	39s
Verify changes (preact-jsx)	42s
Verify changes (preact-tsx)	40s
Verify changes (puppeteer)	39s
Verify changes (playwright)	43s
Verify changes (import-maps)	44s
Verify changes (mock-es-module)	44s
Verify changes (visual-regression)	1s
Verify changes (saucelabs)	16s
Verify changes (guides/test-runner/getting-started)	35s
Verify changes (guides/test-runner/watch-and-debug)	33s
Verify changes (guides/test-runner/playwright)	1m 20s
Verify changes (guides/test-runner/responsive)	47s
Verify changes (guides/test-runner/typescript)	41s
Verify changes (react-htm)	33s
Verify changes (react-jsx)	21s
Verify changes (react-tsx)	21s
Verify changes (snowpack-lit)	16s
Verify changes (snowpack-react)	1s
Verify changes (snowpack-svelte)	13s
	13m 47s

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