s/chromiumos/chromium/ for top level path.

BUG=none
TEST=none

Change-Id: I68522cb225ae45cd4983a10b590b4977195cbfdf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/tast/+/5504009


Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Seewai Fu <seewaifu@google.com>
Auto-Submit: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Seewai Fu <seewaifu@google.com>