rename Chromecast bots to Clang

We updated them to use Clang a while ago but forgot to rename the bots.

Change-Id: I01c353b48d5aff7a30d63d382bdf6bdfb3e0b196
Reviewed-on: https://skia-review.googlesource.com/137887
Auto-Submit: Mike Klein <mtklein@chromium.org>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
11 files changed