[TabbedPane]: Fix focus bug where the placeholder view would steal keyboard focus upon setting
[TabbedPane]: Fix focus bug where the placeholder view would steal keyboard focus upon setting

Issue:
- Sources placeholder view is stealing focus upon instantiation

Changes:
- Remove unnecessary focus call when setting the placeholder view

GIFs:

Before: https://imgur.com/9RefXCS
After: https://imgur.com/LXW6AGJ

Bug: 1045349
Change-Id: Icc9b152798572cfb8d0fe86ccf5e7a18318e96a4
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2148016
Reviewed-by: Shane Clifford <cefa063138c0abe680fc1b6813cf10cbfcb7387b@microsoft.com>
Reviewed-by: Vidal Diazleal <335057fdcb453cd6c3610dd9d7c799602ff689e0@microsoft.com>
Commit-Queue: Vidal Diazleal <335057fdcb453cd6c3610dd9d7c799602ff689e0@microsoft.com>

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