test(material/expansion): fix failing unit test on iOS14 safari
test(material/expansion): fix failing unit test on iOS14 safari

An expansion test seems to be flaky/failing in Safari on iOS14
because the `visibility: hidden` style from the expansion panel
content is not applied immediately. We fix this by enforcing
a style recalulcation like we do in the ripple. An alternative
would have been to switch the test to actual async/await where
we then need to wait at least until the next tick. It seems more
idiomatic to stick with `fakeAsync` here though.

mmalerba/material2,mmalerba/material2,crisbeto/material2,mmalerba/material2,mmalerba/material2,josephperrott/material2,josephperrott/material2,crisbeto/material2,angular/components,angular/components,crisbeto/material2,josephperrott/material2,angular/components,josephperrott/material2,mmalerba/material2,crisbeto/material2,josephperrott/material2,angular/components