DevTools: Remove unnecessary tab stop on workspace mapping
DevTools: Remove unnecessary tab stop on workspace mapping

Removed tabindex from EditFileSystemViews because the stop did not
provide any value after receiving focus.

WCAG 2.7.4 Focus order:
https://www.w3.org/WAI/WCAG21/quickref/#focus-order

NVDA screenshot of removed tab stop:
https://i.imgur.com/sskc4Ac.png

Bug: 963183
Change-Id: Iad7ea3e7a00f44478fbff080e747e110d4615e1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1658631
Reviewed-by: Joel Einbinder <bab755abe9fee48fe544272e55f73517d4e4a725@chromium.org>
Commit-Queue: John Emau <eb1ab95229dc4a7075d47452a0619cbd5cff6c28@microsoft.com>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#674321}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b4769fb4adc31f8b1a0b5bb66d17fb68d7cdcb86

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend