[test] Increase response timeout in `next.browserWithResponse()` (#85911)
The `next.browserWithResponse()` test helper is currently only used in
the `fallback-shells` test suite, which frequently times out after 10
seconds in CI, because the initial compilation for the first request can
take quite a while when there's resource contention. Increasing the
timeout to 30 seconds should help mitigate these issues. We could also
consider removing the timeout entirely. Playwright also doesn't use a
timeout per default for the `page.goto()` method, which we use for
`next.browser()` and `next.browserWithResponse()` under the hood.