Increase cells to 33
Increase cells to 33

We are hovering around 33% advertised capacity remaining on the
cells, which is below the threshold we're aiming for in ARD021[1].
Adding 3 cells beings this back up to around 40%.

[1] https://team-manual.cloud.service.gov.uk/architecture_decision_records/ADR021-cell-capacity-assignment-2/#decision

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