Revert "Use old kaniko executor for now."

This reverts commit 45c2dd5.

I believe the latest is now pointing back to 1.6 until the proper fix is landed.

GoogleContainerTools/kaniko#1791
GoogleContainerTools/kaniko#1794

Author: dancerj

cloudbuild.yaml

@@ -1,5 +1,5 @@
 steps:
-- name: 'gcr.io/kaniko-project/executor:v1.6.0'
+- name: 'gcr.io/kaniko-project/executor:latest'
   args:
     - --destination=gcr.io/$PROJECT_ID/gitlstreefsbuilder
     - --cache=true