Ensure 'task-runner' -> 'toolbox' deprecation notice appears first

What does this MR do?

In #3004 (closed), it was reported that upgrading to chart version 5.5.0 with gitlab.task-runner configuration led to a confusing error message about a valid backup secret being needed. The real problem was that the key should have been changed to gitlab.toolbox.

Related issues

Closes #3004 (closed)

Testing

Values

# ./build/test.values.yaml
global:
  minio:
    enabled: false
  appConfig:
    object_store:
      enabled: false

gitlab:
  task-runner:
    backups:
      objectStorage:
        backend: gcs
        # config:
        #   secret: foo

On master: misleading error

$ helm template test . -f build/test.values.yaml --set certmanager-issuer.email=no@no.com
Error: execution error at (gitlab/charts/gitlab/charts/toolbox/templates/deployment.yaml:227:23): A valid backups.objectStorage.config.secret is needed!

On MR branch: more helpful error

$ helm template test . -f build/test.values.yaml --set certmanager-issuer.email=no@no.com
Error: template: gitlab/templates/NOTES.txt:118:3: executing "gitlab/templates/NOTES.txt" at <include "gitlab.deprecations" .>: error calling include: template: gitlab/templates/_deprecations.tpl:64:46: executing "gitlab.deprecations" at <fail>: error calling fail: HELM_ERR_START
DEPRECATIONS:

gitlab.task-runner:
    The configuration of `gitlab.task-runner` has been renamed. Please use `gitlab.toolbox` instead.HELM_ERR_END

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened

Closes #3004 (closed)