Reland "Remove AssistantState::VISIBLE"

This is a reland of 5072afda30bb50e6a56a1b398632644c8866719b

Original change's description:
> Remove AssistantState::VISIBLE
> 
> Remove the VISIBLE state and use AssistantVisibility instead.
> Also remove obsolete handling for AGSA animations.
> 
> Bug: b/140823590
> Test: Run existing tests
> Change-Id: Id64c5e536dfe6d3e10c9b003c135e76c96a9fee1
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1802819
> Commit-Queue: Yue Li <updowndota@chromium.org>
> Reviewed-by: Sam McNally <sammc@chromium.org>
> Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
> Reviewed-by: Tao Wu <wutao@chromium.org>
> Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#696936}

Bug: b/140823590
Change-Id: Ia161398488e6d920548ade8a1eb37a0a99cc3403
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1832704
Commit-Queue: Yue Li <updowndota@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702095}

diff --git a/ash/shelf/home_button.h b/ash/shelf/home_button.h
index a80f9b352..c7b4a66 100644
--- a/ash/shelf/home_button.h
+++ b/ash/shelf/home_button.h

@@ -49,7 +49,7 @@
 
   // Called when the availability of a long-press gesture may have changed, e.g.
   // when Assistant becomes enabled.
-  void OnVoiceInteractionAvailabilityChanged();
+  void OnAssistantAvailabilityChanged();
 
   // True if the app list is shown for the display containing this button.
   bool IsShowingAppList() const;