Unify on build-tools for istio.io - removing one redundant image (#1675)
Unify on build-tools for istio.io - removing one redundant image (#1675)

The website-tools image has been consolidated into the build-tools
image. As a result, lets remove the usage of this image in the istio.io
documentation repo.

Depends-On: https://github.com/istio/common-files/pull/28/files
Depends-On: https://github.com/istio/tools/pull/272
istio/test-infra,istio/test-infra,istio/test-infra,istio/test-infra