chromeos: Fix DCHECK when opening "App info" from the app list

The settings sub-page "app-management/detail" needs to be in the list
of OS settings sub-pages used by IsOSSettingsSubpage().

Test: Right-click on chrome Web Store app icon and select "App info"
Bug: 1005982
Change-Id: I76202b69843087a627db858c1f5ddf0bc7159790
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1814546
Commit-Queue: James Cook <jamescook@chromium.org>
Commit-Queue: Trent Apted <tapted@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Auto-Submit: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698283}