fix(toast): Update a11y documentation (#4656)

Author: jessebrack

RELEASENOTES.md

@@ -1,6 +1,13 @@
 <!-- Release notes authoring guidelines: http://keepachangelog.com/ -->
 <!-- !!! THIS FILE IS AUTO-GENERATED !!! DO NOT EDIT THIS FILE MANUALLY !!! -->
 
+## Release 2.15.6 - May 5, 2021
+
+## Components
+### [Toast](https://www.lightningdesignsystem.com/components/toast)
+#### Fixed
+- Corrected accessibility information regarding the usage of the `role` attribute.
+
 ## Release 2.15.5 - April 29, 2021
 
 ## Release 2.15.4 - April 27, 2021

ui/components/toast/RELEASENOTES.md

@@ -4,6 +4,12 @@
 
 <!-- ## [Unreleased] -->
 
+## 2.15.6
+
+### Fixed
+
+- Corrected accessibility information regarding the usage of the `role` attribute.
+
 ## 2.14.0
 
 ### Added

ui/components/toast/docs.mdx

@@ -17,7 +17,9 @@ import { getDisplayElementById } from '../../shared/helpers';
 
 ### Accessibility
 
-Notifications should contain `role="status"` on the container to signal to assistive technology that they require the user’s attention. Historically the role of `alert` would be used, but because you can invoke multiple toasts, assertive alerts would override previous toasts in the screen reader's speech queue. Role of `status` is a polite live region, which does not clear the queue, reducing the risk of a toast message being missed.
+Toast should contain `role="alert"` on the container to signal to assistive technology that they require the user’s attention.
+
+When the design uses multiple toasts simultaneously, set the role to `role="status"`. Historically, toasts would use the role of `alert`, but because you can invoke multiple toasts, assertive alerts would override previous toasts in the screen reader's speech queue. The role of `status` is a polite live region, which does not clear the queue, reducing the risk of a missed toast message.
 
 Use a span with `slds-assistive-text` to let the user know what type of notification it is.