chore: fix flaky scroll test

[teemingc]

This PR adds a timeout to ensure the initial scroll has occurred in the browser. It should help with the consistent failures when running the test in vite-ecosystem-ci where the test is too quick and the initial scroll is skipped.

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[dominikg]

do we need a full second here or should we reduce it to 100ms or sth? Also is the same needed after the second scroll? A nicer way could be to await the fact that scrollY is 1000 🤔

[benmccann]

Perhaps you could use page.waitForFunction to avoid a timeout and instead wait for the page position to make it to 1000 pixels?

[benmccann]

I implemented this directly in #12270 using waitForFunction

[benmccann]

Thanks! I'm going to close this in favor of #12270 since that PR is green now