[ios] Do not animate Infobar banner overlay dismissal for cancels

When an animated dismissal is triggered while the user is interacting
with the banner, the dismissal animation is wonky. Since a cancel
indicates the removal of that Overlay request in a non-user generated
manner, it should be ok to just have it removed from the hierarchy.

Bug: 1120706
Change-Id: I3172724ba8121e67838a03ca1b41065b9091654a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2372809
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Auto-Submit: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801145}

ios/chrome/browser/ui/overlays/overlay_presentation_context_impl.mm

@@ -356,8 +356,7 @@ void OverlayPresentationContextImpl::DismissPresentedUI(
   DCHECK(state->coordinator());
 
   state->set_dismissal_reason(reason);
-  bool animate_dismissal = reason == OverlayDismissalReason::kUserInteraction ||
-                           reason == OverlayDismissalReason::kCancellation;
+  bool animate_dismissal = reason == OverlayDismissalReason::kUserInteraction;
   [state->coordinator() stopAnimated:animate_dismissal];
 }