remove the rest of the bazel test wiring for metrics stability

hack/update-generated-stable-metrics.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-# Copyright 2020 The Kubernetes Authors.
+# Copyright 2021 The Kubernetes Authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -23,8 +23,7 @@ set -o nounset
 set -o pipefail
 
 KUBE_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
-export KUBE_ROOT
-
 source "${KUBE_ROOT}/test/instrumentation/stability-utils.sh"
 
 kube::update::stablemetrics
+