graphql: Reference new search backend for latest graphql version

Related to T4464

Test Plan

This does the job:

$ helm install --values values-swh-application-versions.yaml  --values swh/values/default.yaml --values swh/values/staging.yaml swh-test swh --dry-run --debug --set namespace=test 2>&1 | grep -A10 config.yml | head
  config.yml: |
    search:
      cls: remote
      url: http://search0.internal.staging.swh.network:5010
    storage:
      cls: remote
      url: http://webapp.internal.staging.swh.network:5002
    debug: yes

    server-type: wsgi

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Migrated from D8320 (view on Phabricator)