tests: fixed incorrect assertion in movement upgrade test

[mmaslankaprv]

Cover letter

Fixed assertion checking if the number of consumed messages is equal to number of acked ones. Correct assertion should validate if number of consumed messages is greater than equal to number of produced ones as Kafka consumer groups leverage at least once delivery semantics.

Fixes #5888

Backport Required

• [ ] not a bug fix
• [ ] papercut/not impactful enough to backport
• [ ] v22.2.x
• [ ] v22.1.x
• [ ] v21.11.x

UX changes

Describe in plain language how this PR affects an end-user. What topic flags, configuration flags, command line flags, deprecation policies etc are added/changed.

Release notes

[BenPope]

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