Remove fiddle alerts.
Remove fiddle alerts.

They have moved to Managed Prometheus:

https://skia.googlesource.com/k8s-config/+/refs/heads/main/skia-public/fiddle_default_appgroup_alerts.yml

Bug: skia:13542
Change-Id: I3f87483bffb207e5d4e1c87d3147b8e1d80bb411
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/563677
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