Remove sandbox/.

The sandbox/ used be used only in ChromeOS.
Nowadays, it is no longer used, so remove it from the repository.

cf) https://chromium-review.googlesource.com/c/aosp/platform/external/libchrome/+/903207

Bug: None
Test: Build via Treehugger.
Change-Id: I52b79bc2caa8d807cb7a5c37498e3a8b340a625f
168 files changed