Remove cancel_redundant_pipelines_without_hierarchy_cte feature flag and use new code path

drew stachonrequested to merge
use-fast-redundant-cancellation-globally into master

What does this MR do and why?

This MergeRequest removes the old code path for this worker and deletes all the methods that are no longer used. The new code path has been enabled since August 14th without issues.

Rollout issue: #463623 (comment 2047491500)

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Edited by drew stachon

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