Fix flaky test

[rolandgeider]

Currently, nutritional_meal_form_test.dart can be a bit flaky, since we compare the current time so sometimes this fails because the widget was rendered in the next/previous minute. It would be better if we would just mock the current time to whatever value we need

see also
https://pub.dev/packages/clock
https://medium.com/steeple-product/mocking-time-in-flutter-tests-724c42a28daf

[watcher6280]

@rolandgeider Can I work on this one?

[rolandgeider]

sure, go ahead!

I'm not sure if we really need that package though, might be enough to rewrite a bit the test

[watcher6280]

Thanks, I'll add my PR and we can see if it is worth it.