Remove config-file.ConfigMap.yaml from deploy-sourcegraph, prod, dogfood, deploy-sourcegraph-docker

Created by: nicksnyder

# TODO(slimsag): After 3.0 (NOT 3.0-preview), we can remove this. It is
# left here now so that users upgrading to 3.0 will leave it here so
# that the DB will be populated with their old site config file
# (i.e. for migration). This means that for now we have two sources of
# truth for the 'default' cluster configuration: The config-map in this
# repository and the confdefaults.Cluster variable in our main repo.