[App List] Fix crash on MSan bots

AppListClientImplBrowserTest.ActivateSelfDestroyApp test was failing
on MSan bots because a string reference was kept after the string is
destroyed. Updated ChromeAppListModelUpdater::RemoveItem() to copy the
string to the stack.

Bug: 1190347
Change-Id: I717598e7578738772746e5509089296f6a4220f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2776393


Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Yury Khmel <khmel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#864886}