Backport delay in Redis acknowledgement of spec

[woop]

What this PR does / why we need it:
Adds a delay to Redis spec send acknowledgement in order to prevent a race condition with the send event being commited.

Does this PR introduce a user-facing change?:

Occasionally feature sets might enter a pending state due to a race condition with spec acknowledgement. This race has been resolved.

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: woop

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[feast-ci-bot]

@woop: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
test-end-to-end-batch-dataflow	79aabbf	link	/test test-end-to-end-batch-dataflow

Full PR test history

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