Revert "Make 'click' the default action of unfocusable ARIA buttons"

This reverts commit 0e2c9226506a9a4b7223c49b507b0163caab6661.

Reason for revert: Seems to cause failure of All/DumpAccessibilityTreeTest.AccessibilityActionVerbs/linux on some bots

Original change's description:
> Make 'click' the default action of unfocusable ARIA buttons
> 
> Users of ATs on AuraLinux use the default action to know whether or not
> to activate nodes via the keyboard or a simulated mouse event. When a
> node with a button role cannot receive keyboard focus, have the default
> action be click. This heuristic helps ensure that when there is an ARIA
> button that cannot be activated via the keyboard, users know to simulate
> a mouse click.
> 
> Bug: 1025264
> Change-Id: I8f7a79144ba88ef154eb10ead8dd991aed0d659d
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1940331
> Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
> Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
> Reviewed-by: Joanmarie Diggs <jdiggs@igalia.com>
> Cr-Commit-Position: refs/heads/master@{#722165}

TBR=dmazzoni@chromium.org,mrobinson@igalia.com,aleventhal@chromium.org,jdiggs@igalia.com

Change-Id: I851d7e676dd061b9b75dabc9aab0a4f768ae6e49
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1025264, 1031319
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1953387
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#722270}