message: Set the flag only to true.
  A return value of true means that the structure was modified, and we
  should persist changes to the bids collection.
diff: @@ -364,7 +364,9 @@ pub trait Auction:
  // Process bids
  let mut bids_modified = false;
  for (validator_public_key, bid) in bids.iter_mut() {
  - bids_modified = bid.process(era_end_timestamp_millis);
  + if bid.process(era_end_timestamp_millis) {
  + bids_modified = true;
  + }
  if evicted_validators.contains(validator_public_key) {
  bids_modified = bid.deactivate()
  