Tweak smart selection animation

Result(with ag/12911059 as well):
https://recall.googleplex.com/projects/ea8c4705-96bd-46f0-9f37-786708050727

1. Removed the corner animators.
Before 3552167, we supported two modes - fit and overshoot.
In fit mode, the highlight is expanded to a rounded rectangle.
Then corner animator then fills the corner so that the highlight
becomes a rectangle.
In overshoot mode, the expansion animation ends up in a rectangular
highlight, so the corner animator is just like doing no-op for 50ms.

With ag/3552167, we deleted the fit mode and ended up using the overshoot
mode. So, the corner animator is no longer necessary. Deleting it
saves 50ms. I confirmed that it is a no-op by increasing the duration of
it to be 5s.

2. Before this CL, the whole animation takes 350ms.
As per the material design spec
(https://material.io/design/motion/speed.html#duration)
small animation(e.g. toggle) takes 100ms
medium animation(bottom sheet) takes 250ms
large animation(page transition) takes 300 ms.
That means, our animation takes even longer than the large animation!
I think smart selection animation is somewhere between small
and medium, so adjusted the animation duration to be 200ms.

Bug: 169043706

Test: Manual. Select the text and observe the animation.

Change-Id: Ib32bb47851c1cfe95d6951998d6dc5c09a37e17b