[router]: cancel ExpoRouter SplashScreen during test teardown (#27620)

# Why

#27512 is causing extra console logging due to the
`requestAnimationFrame` used by Expo Router to hide the splash screen.
Previously this logic was never invoked as we were using fake timers,
but now we need to cancel the timeout so it doesn't run after the tests
have ended.

# How

Added a `cleanup()` to `expo-router/testing-library` that removes the
`requestAnimationFrame` if it has not run yet.

# Test Plan

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# Checklist

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- [ ] Documentation is up to date to reflect these changes (eg:
https://docs.expo.dev and README.md).
- [ ] Conforms with the [Documentation Writing Style
Guide](https://github.com/expo/expo/blob/main/guides/Expo%20Documentation%20Writing%20Style%20Guide.md)
- [ ] This diff will work correctly for `npx expo prebuild` & EAS Build
(eg: updated a module plugin).

---------

Co-authored-by: Expo Bot <34669131+expo-bot@users.noreply.github.com>

packages/expo-router/CHANGELOG.md

@@ -25,6 +25,7 @@
 - Fix incorrect route generation of array shared groups with brackets ([#27459](https://github.com/expo/expo/pull/27459) by [@marklawlor](https://github.com/marklawlor))
 - Remove `jest.fakeTimers()` from `expo-router/testing-library` ([#27512](https://github.com/expo/expo/pull/27512) by [@marklawlor](https://github.com/marklawlor))
 - Fix incorrect initial URL on web when using baseUrl ([#27287](https://github.com/expo/expo/pull/27287) by [@marklawlor](https://github.com/marklawlor))
+- Cancel ExpoRouter SplashScreen during test teardown ([#27620](https://github.com/expo/expo/pull/27620) by [@marklawlor](https://github.com/marklawlor))
 
 ### 💡 Others