chore: bump @progress/wct-a11y-spec from 2.19.1 to 2.20.0 in /src-a11y (#3410)

* chore: bump @progress/wct-a11y-spec from 2.19.1 to 2.20.0 in /src-a11y

Bumps [@progress/wct-a11y-spec](https://github.com/telerik/web-components-ux) from 2.19.1 to 2.20.0.
- [Commits](https://github.com/telerik/web-components-ux/commits)

---
updated-dependencies:
- dependency-name: "@progress/wct-a11y-spec"
  dependency-version: 2.20.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

* docs: update accessibility and keyboard-nav specs

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: kendo-bot <kendouiteam@progress.com>

Author: dependabot[bot]

components/tilelayout/accessibility/wai-aria-support.md

@@ -30,8 +30,6 @@ This section lists the selectors, attributes, and behavior patterns supported by
 |  | `aria-labelledby` | Associates the focusable item wrapper with the respective header text element (.k-tilelayout-item-header .k-card-title). |
 |  | `tabindex=0` | Makes the item wrapper element focusable. |
 |  | `aria-keyshortcuts=Enter` | Announces Enter as an available key shortcut when the item is focused. |
-|  | `aria-dropeffect=execute` | Announces that an action, supported by the drop-target (resizing or reordering) will be executed when the item is dropped. |
-|  | `aria-grabbed=true/false` | The "aria-grabbed" state indicates an element's 'grabbed' state in a drag-and-drop operation. |
 | `.k-tilelayout-item-header .k-card-title` | `id` | Unique and deterministic identifier to link the header text element to the focusable wrapper. |
 
 ## Section 508

src-a11y/package-lock.json

@@ -8,7 +8,7 @@
   "author": "",
   "license": "ISC",
   "devDependencies": {
-    "@progress/wct-a11y-spec": "^2.19.1",
+    "@progress/wct-a11y-spec": "^2.20.0",
     "gulp": "^4.0.2",
     "gulp-json-editor": "^2.5.6",
     "gulp-rename": "^2.0.0",