Move presubmit bot to skia.swarmbucket

BUG=skia:6183

Change-Id: Ib678c83f46f453b561101cdc12ee637a4e51fb17
Reviewed-on: https://skia-review.googlesource.com/7863
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
1 file changed