added cap on undelegate messages (#940)

Closes: #XXX

## Context and purpose of the change




## Brief Changelog




## Author's Checklist

I have...

- [ ] Run and PASSED locally all GAIA integration tests
- [ ] If the change is contentful, I either:
    - [ ] Added a new unit test OR 
    - [ ] Added test cases to existing unit tests
- [ ] OR this change is a trivial rework / code cleanup without any test coverage

If skipped any of the tests above, explain.


## Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] manually tested (if applicable)
- [ ] confirmed the author wrote unit tests for new logic
- [ ] reviewed documentation exists and is accurate


## Documentation and Release Note

  - [ ] Does this pull request introduce a new feature or user-facing behavior changes? 
  - [ ] Is a relevant changelog entry added to the `Unreleased` section in `CHANGELOG.md`?
  - [ ] This pull request updates existing proto field values (and require a backend and frontend migration)? 
  - [ ] Does this pull request change existing proto field names (and require a frontend migration)?
  How is the feature or change documented? 
      - [ ] not applicable
      - [ ] jira ticket `XXX` 
      - [ ] specification (`x/<module>/spec/`) 
      - [ ] README.md 
      - [ ] not documented

x/stakeibc/keeper/unbonding_records.go

@@ -301,6 +301,10 @@ func (k Keeper) UnbondFromHostZone(ctx sdk.Context, hostZone types.HostZone) err
 		return errorsmod.Wrap(sdkerrors.ErrInvalidRequest, "Target unbonded amount was 0 for each validator")
 	}
 
+	if len(msgs) > UndelegateICABatchSize {
+		return errorsmod.Wrapf(sdkerrors.ErrInvalidRequest, fmt.Sprintf("too many undelegation messages (%d) for host zone %s", len(msgs), hostZone.ChainId))
+	}
+
 	// Send the messages in batches so the gas limit isn't exceedeed
 	for start := 0; start < len(msgs); start += UndelegateICABatchSize {
 		end := start + UndelegateICABatchSize