fix(runner): async assertion auto await should timeout

[hi-ogawa]

Description

• closes https://github.com/vitest-dev/vitest/issues/6386

Currently documentation indicates resolves/rejects needs to be manually awaited https://vitest.dev/api/expect.html#resolves, but "auto await" mechanism is added along with toMatchFileSnapshot https://github.com/vitest-dev/vitest/pull/3116/. It looks like the intent is to make "sync" API, so the documentation is outdated, but I'm not sure if we should encourage this "sync" API because it doesn't feel really intuitive anyway.

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