[Java] MapWithOrdinal javadoc doesn't describe actual behaviour

MapWithOrdinal states that ordinals are recycled when keys are removed, it does not currently do this and grows unbounded

**Reporter**: [Ryan Murray](https://issues.apache.org/jira/browse/ARROW-8947) / @rymurr
#### PRs and other links:
- [GitHub Pull Request apache/arrow#7276](https://github.com/apache/arrow/pull/7276)

_{**Note**: *This issue was originally created as [ARROW-8947](https://issues.apache.org/jira/browse/ARROW-8947). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start with the MapWithOrdinal Javadoc and review the linked pull request apache/arrow#7276 to understand the intended documentation change. Done means the Javadoc accurately describes whether ordinals are recycled when keys are removed and no longer contradicts the implementation.

Written by the indexing model from the issue text.