dashboard: disable Kubernetes builders
dashboard: disable Kubernetes builders

Updates golang/go#14112

Change-Id: Ie45029e27d8d8ce421135cc0e38f7019965bfa34
Reviewed-on: https://go-review.googlesource.com/18990
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

golang/build,proppy/build,proppy/build,golang/build,golang/build,golang/build,proppy/build,proppy/build