Remove unused complete field from pipeline query

What does this MR do?

We are not using the complete field right now anywhere and its throwing an error when we fetch pipelines. Most likely because the BE was introduced introduced together with the frontend query. See original issue: !61209 (merged)

Here is the sentry error: https://sentry.gitlab.net/gitlab/gitlabcom-clientside/issues/2639006/?query=is%3Aunresolved

Screenshots (strongly suggested)

none

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