Revert "Feature flag cleanup - `bulk_imports_batched_import_export`"

What does this MR do and why?

Revert "Merge branch 'bmarjanovic/feature-flag-rollout-bulk_imports_batched_import_export' into 'master'"

This reverts merge request !132537 (merged)

Note: According to ChatOps, the feature flag still exists in production and is enabled. So, reverting the MR shouldn't impact inflight migrations

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