[infra] Remove old power build target
[infra] Remove old power build target

Change-Id: I07531a7997d75311e45d71ef26290f2dd43a5554
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/454717
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot